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Only individuals ha\ c a sense of responsibility — Nutzschb 

T HIS book does not represent a complete collection 
of the articles, addresses and pronouncements of 
Albert Einstein , it is a selection made with a definite 
object, nimel) , to give a picture of a man To-day this 
man is being drawn, contrary to his own intention, into 
the whirlpool of political passions and contemporary his- 
tory As a result, Einstein is experiencing the fate that 
so many of the great men of history experienced Ins 
character and opinions are being exhibited to the world 
in an utterly distorted form 
To forestall this fate is the real object of this book It 
meets a wish that has constantly been expressed both 
by Einsteins friends and by die wider public It con- 
tains work belonging to the most various dates— the 
article on “The International of Science” dates from 
the year 1922, the address on “The pnnciplds of Scien- 
tific Research” from 1923, the “Letter to an Arab” 
from 1930 — and die most various spheres, held together 
by the unity of the personality which stands behind all 
these utterances Albert Einstein believes in humanity, 
in a peaceful world of mutual helpfulness, and in the 
high mission of science This book is intended as a plea 
for this belief at a time which compels every one of us 
to overhaul his mental attitude and his ideas ' 




In Part V I have had the benefit of the 
expert supervision of Dr. H. 'Stafford 
Hatfield, to whom my thanks are due. 



PART 1^ 

The World, as I see it 


The Meaning of Life i 

The World as I see it I 

The Liberty of Doctrine — a propos of the Gumbel Case J 

Good and Evil 7 

The True Value of a Human Being 7 

Society and Personality 7 

Address at the Grave of H A Lorentz 11 

H A Lorentz's work m the cause of Intemanonal 
Co-operation rr 

In Honour of Arnold Berliner's Seventieth Birthday 14 
Popper Lynkaeus 16 

Obituary of the Surgeon, M Katzenstein 16 

Congratulations to Dr Solf 19 

Of Wealth 2o 

Education and Educators 21 

To the Schoolchildren of Japan 21 

Teachers and Pupils 22* 

Paradise Lost 23 

Religion and Science 23 

The Religiousness of Science 2 g 

The Plight of Science 2 g 

Fascism and Science » 

Thanks to America 




Par: I— continued • 

The University Count at Davos . 
Congratulations to a Cnric . 

Greeting to G Bernard Shaw 

Some Notes on my American Impressions 

Reply to the Women of America . 








Politics and Pacitom 

Peace 45 

The .Pacifist Problem 45 

Address to the Students’ Disarmament Meeting . 4 6 

To Sigmund Freud 48 

Compulsory Service . . .' . .50 

Germany and France .... • 5 t 

Arbitration . .... J2 

The Intcrnanonal of Science ... -52 

The Institute For Intellectual Co-opcranon . . 54 

A Farewell .56 

The Question oF Disarmament . . 57 

The Disarmament Conference oF 1932 J8 

America and the Disarmament ConFerence . . 65 

Acnve Pacifism 67 

Letter to a friend of Peace ...... 68 

Another ditto ....... 69 

A third ditto ....... 70 

Women and War . . . ... 71 

Thoughts on the World Economic Cnsis . . 71 

Culture and Prosperity ...... 76 



Part II— continued * PAGE 

„ Production and Purchasing Power ... 77 

Production and Work . * • *78 

Minorities “ • .80 

Observations on the Present Situation in Europe . 80 

The Heirs of the Ages 81 


Germany 1933 

Manifesto '• -85 

Correspondence with the Prussian Academy of Sciences 85 
A Reply 92 

The Jews 


Jewish Ideals 

Is there a Jewish point of view t 

Jewish Youth — An Answer to a Questionnaire. 

Addresses on Reconstruction in Palestine. 

The Jewish Community .... 

.Working Palestine 

Jewish Recovery 

Anti-Semitism and Academic Youth 
A Letter to Peofesxrr Dr. HnVpa eft, Minister of State 

Tenet to an Arab 

Christianity arid Judaism 
A Foreword ... 












II 8 





Principles of Scientific Research 123 

Inaugural Address to the Prussian Acadcni) of Sciences 
(* 9 * 4 ) . 127 

Scientific Truth 13 1 

The Method of Theoretical Physics 131 

Address at Columbia University, New York 139 

Johannes Kepler 141 

The Mechanics of Newton and their Influence on the 
1 Development of Theoretical Physics 146 

Clerk Maxwell s Influence on the Evolution of the Idea 
of Physical Rea hf} 156 

Niels Bohr . 162 

On the Theory of Relativity 1 63 

What is the Theory of Relanvity ? 1 66 

The Problem of Space, Ether and the Field in Physics 173 
Notes on the origin of the general theory of Relanvity 187 
Relanvit) and the Ether 193 

The cause of the formation of meanders in the courses 
of nvers and of Beer s Law., as it jis called 204 

The Fletmer ship 209 


The Meaning oj Life 

W HAT is the meaning of human life, or of organic 
life altogether? To answer this question at all 
implies a religion Is there any sense then, you ask, in 
putting it ? I answer, the man who regards his own life 
and that of his fellow-creatures as meaningless is not 
merely unfortunate but almost disqualified for life 

The World as I see it 

What an extraordinary situation is that of us mortals * 
Each of us is here for a brief sojourn, for what purpose 
he knows not, though he sometimes thinks he feels it 
But from die point of view of daily life, without going 
deeper, we exist for our fellow-men — in the first place 
for those on whose smiles and welfare all our happiness 
depends, and next for all those unknown to us personally 
with whose destinies we are bound up by the tie of 
sympathy A hundred times every day I remind myself r 
that my inner and outer life depend on the labours of. 
other men, living and dead, and that I must exert myself 
m order to give in the same measure as I have received 
and am* still receiving I am strongly drawn to the 
simple life and am often oppressed by the feeling that I 
am engrossing an unnecessary amount of the labour of 
my fellow-men I regard class differences as contrary 
to justice and, in the last resort, based on force I also 
consider that plain living is good for everybody, 

„ physically and mentally - 

my own gait and have never belonged to ms _ 
m> home, my friends, or even my^medute S’ 

Amh my whole heart , nr dre face of aU these ucs i & - 
never lost an ohsnnate seme of detachment, of the nS d 
for solitude— a feelrng winch mcreases wad, 

One is sharply conscious yet without regret " 
limits to the possibility of mutual -understand,*, , 
sympathy with one s fellow -creatures Such a 8 
no doubt loses something in the wav nf i P crson ^ 

hght-heartedness , on the odier handle nTamd? J ? d 

pendent of the opuuons, habits and judgment? 'ref 
fellows and avoids the temptanon to talc his sta d d 
such insecure foundations °n* 

My polincal ideal is that of democracy Le t . y 
man be respected as an individual and no man , A^ Ct ) \ 
It is an irony of fate that I myself have been the rean 
of excessive admiration and respect from my fJ} 1Cnt 
through no fault and no ment, of my own The 
of this may well be the desire, unattainable for m^f 
to understand die one or two ideas to which I have JX 
my feeble powers attained through ceaseless struf>oI 
I am quite aware that it is necessary for the succcs * * 
of any complex undertaking that one man should do the 
thinking and directing and m general bear the respon- » 
sibility But die led must not be compelled, they must * 
be able to choose their leader An autocratic system of 
:oeraon, in my opinion soon degenerates For force 
Jways attracts men of low morality', and I believe it to 
je an invariable rule that tyrants of genius are succeeded 
iy scoundrels For this reason I have always been pas 
iionatcly opposed to systems such as wc see m Italy and 
Russia to-day The dung that has brought discredit 
upon the prevailing form of democracy m Europe to- 
day is not to be laid to the door of the democratic idea 


In human freedom in the philosophical sense I am 
definitely a disbeliever. Everybody acts not only under 
external compulsion but also in accordance with inner 
necessity. Schopenhauer’s saying, that “a man can do 
as he will, but not will as *he will,” has been an 
inspiration to me since my youth up, and a continual 
consolation and unfailing well-spring of patience in the' 
face of the hardships of life, my own and others’. Tliis 
feeling mercifully mitigates the sense of responsibility 
which so easily becomes paralysing, and it prevents us 
from taking ourselves and other people too seriously; 
it conduces to a view of life in which humour, above 
all, has its due place. ' 

To enquire after the meaning or object of one's own 
existence or of creation generally has always seemed to 
me absurd from an objective point of view. And yet 
everybody has certain ideals which determine the direc- 
tion of his endeavours and his judgments. In this sense 
I have never looked upon ease and happiness as’ends in 
themselves — such an ethical basis I call more proper for 
i a herd of swine. The ideals which have lighted me on 
my way and nmc after time given me new courage to 
face life cheerfully, have been Truth, Goodness and 
Beauty. Without the sense of fellowship with men 'of 
like mind, of preoccupation with the objective, the 
* eternally unattainable in the field of art and scientific 
research, life would have seemed to me empty. The > 
ordinary objects of human endeavour— propetty, out- 
ward success, luxury — have always 'seemed to me 

My passionate seme of social justice and social res- 
ponsibility has_ always eontnmed_ oddlv* with my pro- 
nounced freedom from the need for direct contact with 
other human beings and human communities. I pane 
2 ’ J 


my own gait and have never belonged to my country, 
my home, my friends, or even my immediate family, 

I with my whole heart; in the face of all these tics I have 
I never lost an obstinate sense of detachment, of die need 
f for solitude— a feeling which increases with die years. ■ 
f One is sharply conscious, yet without regret, of die 
limits to die -possibility of mutual understanding and 
sympathy with one’s fcllow'-crcaturcs. Such a person) 
no doubt loses something in the way of geniality and! 
light-hcartcdncss ; on the other hand, he is largely inde-l 
pendent of the opinions, habits and judgments of his! 
fellows and avoids the temptation to take his stand on* 
such insecure foundations. 

My political ideal is that of democracy. Let every 
man be respected as an individual and no man idolised. 
It is an irony of fate that I myself have been die recipient 
of excessive admiration and respect from my fellows 
through no fault, and no merit, of my own. The cause 
of this may well be the desire, unattainable for many, 
to understand the one or two ideas to which I have with 
my feeble powers attained through ceaseless struggle.*' 
I am quite aware that it is necessary for the success 
of any complex undertaking that one man should do the 
thinking and directing and in general bear the respon- 
sibility. But the led must not be compelled, diey must 
be able to choose their leader. An autocratic system of 
coercion; in my opinion, soon degenerates. For force 
always attracts men of low morality, and I believe it to 
be an invariable rule that tyrants of genius are succeeded 
by scoundrels. For this reason I have always been pas- 
sionately opposed to 
Russia to-day. The 
upon the prevailing 
day is not to be laid 


systems such as we see in Italy and 
thing that has brought discredit 
torm of democracy in Europe to- 
to the door of die democratic idea 


as such, but to lack of stability on the part of the heads 
of governments and to the 'impersonal character of the 
electoral system. I believe that in this respect the United 
States of America have found the right way. They have 
a responsible President who is elected for a sufficiently 
long period and has sufficient powers to be really 
responsible. .On the other hand, what I* value m our 
political system is the more extensive provision that it 
makes for the individual in case of illness or need The 
really valuable thing in the pageant of human life seems. 
I to me not the state but the creative, sentient individual, 
i the personality; it alone creates the noble and the 
sublime, while the herd as such remains dull in thought 
and dull m feeling 

This topic brings me to that worst outcrop of the 
herd nature, the military system, which I abhor. That a 
man can take pleasure in marching in formation to the 
strains of a band is enough to make me despise him. He 
has only been given his big brain by mistake; a back- 
bone was all he needed. This plague-spot of civilisa- 
tion ought to be abolished with all possible speed. 
Heroism by order, senseless violence and all the pestilent 
nonsense that goes by the name of patriotism — hoW I 
hate them! War seems to me a mean, contemptible 
thing . I would father be hacked in pieces than take part 
in such an abominable business And yet so high, in 
spite of ever} dung, is my opinion of the human race 
that I believe dm bogey would have disappeared long 
ago, had the sound sense of the nations not been 
systematically corrupted by commercial and political 
interests acting through die schools and the Press 

Tine fairest Aung we can experience is the my stenous 
It is the fundamental emotion which stands at the cradle 
of true art and true science. He who knows it not and 
, r 


can no longer wonder, no longer feel amazement, is as 
good as dead, a snuffed-out candle ft was the ex- 
perience of mystcr) — even if mixed with fear — that 
engendered religion A knowledge of the existence of 
something we cannot penetrate, of the manifestations of 
the profoundcst reason and the most radiant beauty, 
which arc only accessible to our reason in their most 
elementary forms— it is dus knowledge and this emo- 
tion that constitute die truly religious attitude , m dus 
sense, and m dus alone, I am a deeply religious man I 
cannot conceive of a God who rewards and punishes his 
creatures, or has a will of the type of which wc arc 
conscious m ourselves An individual^ who should 
survive his physical dcadi is also beyond my compre- 
hension, nor do I wish it otherwise, such notions arc for 
the fears or absurd egoism of feeble souls Enough for 
me the mystery of die eternity of life, and the inkling 
of the marvellous structure of reality, together with die 
single-hearted endeavour to comprehend a portion, be 
it never so any, of the reason that manifests itself in 

The Liberty of Doctrine— a propos of the Gumbcl Case 

Academic chairs arc many, ,but \fase and noble 
teachers are few, lecture-rooms are numerous and large, 
but the number of young people who genuinely thirst 
after truth and jusace is small Nature scatters her com- 
mon wares with a lavish hand, but die choice sort she 
produces but seldom 

We t aU kn J ow *“• 50 wJ >y complain; Was it not 
cvct thus and will it not ever thus remain > Certainly 
and one mus t take what nature gives as one finds it 
But there is also such a thing as a spirit of the nmes an 


attitude of mind characteristic of a particular generation, 
which is passed on from individual to individual and 
gives a society its particular tone Each of us has to do 
his little bit towards transforming this spirit of the times 

Compare the spirit which animated the youth in our 
universities a hundred years ago with that prevailing 
to-day They had faith m the amelioration of human 
society , respect for every honest opinion, the tolerance 
for which our classics had lived and fought In those 
days men strove for a larger political unity, which at 
that time was called Germany It was the students and 
the teachers at the universities who kept these ideals 

To-day also there is an urge towards soaal progress, 
towards tolerance and freedom of thought, towards a 
larger political unity , which wc to-day cdl Europe But 
the students at our umv ersmes have ceased as completely 
as their teachers to enshnne the hopes and ideals of the 
nation Anyone who looks at our times coolly and dis- 
passionately must admit this 

Wc arc assembled to-day to take stock of ourselves 
The external reason for <thu meeting is the Gumbcl 
case This aposde of justice has written about unex- 
piatcd political enmes with devoted industry, high 
courage, and exemplary fairness, and has done the com- 
munity a signal service by his books And this is the 
man whom die students, and a good many of the staff, 
of his university are to-day doing their best to expel 

Political passion cannot be allowed to go to such 
lengths I im convinced dm every man who reads 
Herr Gumbcl’s books uidi an open mind will gci the 
same impression from diem as I have Men like fum 
arc needed if wc arc ever to build up a healdiy political 



Let every man judge according to his own. standards, 
by what he has himself read, not by what others tell 

If that happens, this Gumbel case, after an unedifying 
beginning, may still do good. 

Good and Evil 

It is right in principle that those should be the best 
loved who have contributed most to the elevation of 
the human race and human life. But if one goes on to 
-ask who they are, one finds oneself in no inconsiderable 
difficulties. In the case of political, and even of religious, 
leaders, it is often very doubtful whether they have done 
more good or harm. Hence I most seriously believe that 
one does people the best service by giving them some- 
elevating work. -to do and thus indirectly elevating them. 
This applies most of all to the great artist, but also in a 
’ lesser degree to the scientist. To be sure, it is not the 
fruits of scientific research that elevate a man and enrich 
his nature, but the urge to understand, the intellectual 
work, creative or receptive. It would surely be absurd 
to judge the value of the Talmud, for instance, by its 
* intellectual fruits. 

The true value of a human being is determined primarily 
by the measure and the sense in which he has attained 
to liberation from the self. 

Society and Personality 

When we survey our Iives'and endeavours we soc 
observe that almost the whole of our actions and desir 
are bound up wuh the existence of other human being 


We see that our whole nature resembles that of the 
social animals. We eat food that others have grown, 
wear clothes that others have made, live in houses that 
others have built. The greater parr of our knowledge 
and beliefs has been communicated to us by other 
people through the medium of a language which others 
have created. Without language our mental capacities 
would be poor indeed; comparable to those of the 
higher animals; we have, therefore, to admit that we 
owe our principal advantage over the beasts to the fact 
of living in human society. The individual, if left alone 
from birth, would remain primitive and beast-hke in. 
his thoughts and feelings to a degree that we can hardly 
conceive. The individual is what he is and has the 
significance that he has not so much in virtue of his 
individuality, but rather as a member of a great human 
society, which directs his material and spiritual existence 
from the cradle to the grave. 

A man’s .value to the community depends primarily 
on how far his feelings, thoughts and actions arc 
directed towards promoting the good of his fellows. 
Wc call him good or bad according to how he stands 
in tHis matter. It looks at fine sight as if our estimate of 
a man depended entirely on his social quah des. 

And yet such an attitude would be wrong. It is clear 
that all the valuable things, material, spiritual and moral, 
which we receive from society can be traced back 
through countless generations to certain creative in- 
dividuals. The use of fire, die cultivation of edible 
plants, die steam engine; — cadi was discovered by one 

Only the individual can think, and thereby create 
new values for -sodety, nay, even set up new moral 
standards to which the life of the community; conforms. __ 


Without creative, independently thinking and judging 
personalities the upward development of society is as 
untliinkable as the development 'of the individual 
personality without the nourishihg soil of the com- 

The health of society thus depends quite as much on 
the independence of the individuals composing it as on 
*their close political cohesion. It has been said very 
justly that Graxo-Europeo-American culture as a. 
whole, and in particular its brilliant flowering in the 
Italian Renaissance, which put an end to die stagnation 
of mediaeval Europe, is based oil the liberation and 
comparative isolation of the individual. 

Let us now consider the times in which we live. 
How docs society fare, how the individual i The popu- 
lation of the civilised countries is extremely dense as 
compared with former times; Europe to-day contains 
about three times as many people 'as it did a hundred 
years ago. But. the number of great men has decreased 
out of all proportion. Only a few individuals are known 
to the masses as personalities, through their creative 
achievements. Organisation has to some extent taken 
the place of the great man, particularly in the technical 
sphere, but also to a very perceptible extent in the 

The lack of outstanding figures is particularly striking 
in the domain of art. Painting and music have definitely 
degenerated and largely lost their popular appeal.* In 
politics not only are leaders lacking, but the indepen- 
dence of spirit and the sense of justice of the citizen 
have to a great extent declined. The democratic, parlia- 
mentarian regime, which is based on such independence 
has in many places .been shaken, dictatorships have 
sprung up and are tolerated, because men’s sense of the 


dignity and the rights of the individual is no longer 
strong enough In two weeks the sheep-hke masses can 
be worked up by the newspapers into juch a state of 
excited fury that the men are prepared to put on 
uniform and kill and be killed, for the sake of the 
worthless aims of a few interested parties Compulsory 
military service seems to > me the most disgraceful 
symptom of that deficiency in personal dignity from 
which civilised mankind is suffering to-day No won- 
der there is no lack of prophets who prophesy the 
early eclipse of our avihsanon I am not one of diesc 
pessimists , I believe that bettdr times arc coming Let 
me shortly state my reasons for such confidence 
In my opinion, the present symptoms of decadence 
are explained by the fact that the development of 
industry and machinery has made the struggle for 
existence very’ much more severe, greatly to the detri- 
ment of die free development of the individual Bur 
the de\elopmem of machinery means diat less and less 
work is needed from, the uidividual for die satisfaction 
of the comm unit) ’s needs A planned division of labour 
is becoming more and more of a crying necessity, and 
this division will lead to die material security of die 
m dividual This security and the spare time and energy 
which the individual will have at his command can be 
made to further his development In this way die 
community may regain its health, and we will hope 
that future historians will explain die morbid symptoms 
of present-day society ar the childhood ailments of an 
aspiring humanity, due entirely to the excessive speed at 
which civilisation was advancing 



Address at the Grave of H. A. Lorentz 

It is as the representative of the German-speaking 
academic world and in particular the Prussian Academy 
of Sciences, but above all as a pupil and affectionate 
admirer that I stand at the grave of the greatest and 
noblest man of our times. # His genius was the torch 
which lighted die way from the teachings of Clerk 
Maxwell to die achievements of contemporary physics, 
to the fabric of which he contributed valuable materials 
and methods. 

His life was ordered like a work of art down to dip 
smallest detail. His never-failing kindness and mag- 
nanimity and his sense of justice, coupled with an 
intuitive understanding of people and tilings, made him 
a leader in any sphere he entered. Everyone followed 
him gladly, for dicy felt diat he never set out to dominate 
but always simply to be of use. His work and his 
example will live on as an inspiration and guide to 
future generations. 

H. A. Lorentz s work in the cause of International 
s Co-operation 

With die extensive specialisation of scientific research 
which the nineteenth century brought about, it lias 
become rare for a man occupying a leading position in 
one of the sciences to manage at die same time to do 
valuable service to the community in the sphere t>f 
international organisation and international politics. 
Such service demands not only energy, insight and a 
reputation based on solid achievements, but also a 
freedom from national prejudice and a devotion to the 
common ends of all, which have become rare in our 
* II 


dines I have met no one who combined all these 
qualities m himself so perfectly as H A Lorcntz. The 
marvellous thing about the effect ofhis personality was 
this — Independent and headstrong natures, such as are 
particularly common among men of learning, do not 
readily bow to another* s will and for the most pan only 
accept his leadership grudgingly But when Lorcntz 
is in the presidential chair, an atmosphere of happy 
co-operation is invariably created, however much those 
present may differ in their aims and habits of thought 
The secret of this success lies not only m his swift com- 
prehension of people and things and his marvellous 
command of language, but above all in this, that one 
feels that his whole heart is m the business in hand, and 
that when he is at work, he has room for nothing else 
m his mind Nothing disarms the recalcitrant so much 
as this 

Before the War Lorcntz’s activities in the cause of 
international relations were confined to presiding at 
congresses of physicists Particularly noteworthy among 
these were the Solvay Congresses, the first two of 
which were held at Brussels in 1909 and 1912 Then 
came the European war, which was a crushing blow to 
all who had the improvement of human relations in 
general at heart Even before the vva- was over, and 
soil more after its end, Lorcntz devoted himself to the 
work of reconciliation His efforts were especially 
directed towards the re-estabhshment of fruitful and 
friendly co-operanon between men of learning and 
scientific societies An outsider can hardly conceive 
what uphill work this is The accumulated resentment 
of the war period has not yet died down and many 
influential men pen 1st in the irreconcilable attitude into 
which they allowed themselves to be driven by the 


pressure of circumstances. Hence Lorentzs efforts 
resemble those of 3 doctor' with a recalcitrant patient 
who refuses to take the medicines carefully prepared 
for his benefit. 

But Lorentz is not to be deterred, once he has recog- 
nised a course of action as the right one. The moment 
the war was over, he joined the governing body of the 
“Conseil de recherche” which -was founded by the 
savants of the victorious countries, and from which the 
savants and learned societies of the Central Powers were 
excluded. His object in taking this -step, which caused 
great offence to the academic world of the Central 
Powers, was to influence this institution in such a way 
that it could be expanded into something truly inter- 
national. He and other right-minded men succeeded, 
after repeated efforts, in securing the removal- of the 
offensive exclusion-clause from the statutes of the 
“Conscil” -The goal, which is the restoration of 
normal and fruitful co-operation between learned 
societies, is, however, not yet attained, because the 
academic world of the Central Powers, exasperated by 
nearly ten years of exclusion from practically all inter- 
national gatherings, has got into a habit of keeping 
itself to itself. Now, however, there are good grounds 
for hoping that the ice will soon be broken, thanks to 
the tactful efforts of Lorentz, prompted by pure 
enthusiasm for the good cause. 

Lorentz has also devoted his energies to the service 
of international cultural ends in another way, by con- 
senting to serve on the League of Nations Commission 
for international intellectual co-operation, which was 
called into existence some five years ago with Bergson 
as chairman. For the last year Lorentz has presided over 
the Commission, which, with the active support of its 


subordinate, the Paris Institute, is to act as a go-between 
• in the domain of intellectual and artistic work among 
the various spheres of culture. There too the beneficent 
; influence of this intelligent, humane and modest per- 
\ sonality, whose unspoken but faithfully followed advice 
J is, ‘'Not mastery but service,” will lead people in the 
right way. 

, May his example contribute to the triumph of that 

In Honour of Arnold Berliner's Seventieth Birthday 
(Arnold Berliner is the editor of the periodical Die Natimvissen- 

I should like to take this opportunity of* telling my 
friend Berliner and the readers of this paper why I rate 
him and his work so highly. It h^s to be done here 
because it is one’s only chance of getting such things 
said ; since our training in objectivity has Jed to a taboo 
on everything personal, which we mortals may only 
transgress on quite exceptional occasions such as the 
present one. 

And now, after this dash for liberty, back to the 
objective! The province of srienrifically determined 
fact has been enormously extended, theoretical know- 
ledge has become vastly more profound in every' 
department of science. But the assimilative power of the 
human intellect is and remains strictly limited. Hence 
it was inevitable that the activity of the individual 
investigator should be confined to a smaller and smaller 
section of human knowledge. Worse still, as a result 
of tliis specialisation it is becoming increasingly difficult 
for even a rough general grasp of science as a whole, 
without which the true spirit of research is inevitably 


handicapped, to keep pace with progress A situation is 
developing similar to the one symbolically represented’ 
in the Bible by the story of the Tower of Baba Every 
serious scientific worker is painfully conscious of this 
involuntary relegation to an ever-narrowing sphere of 
knowledge, which is direatemng to deprive the investi- 
gator of his broad horizon and degrade him to the 
level of a mechanic 

"We have all suffered under this evil, without making 
any effort to mitigate it But Berliner has come to the 
rescue, as far as the German-speaking world is con- 
cerned, in the most admirable way He saw that the 
existing popular periodicals were sufficient to instruct 
and stimulate the layman, hut he also saw that a fust- 
class, well-edited organ was needed for the guidance of 
the scientific worker who desired to be put sufficient!) 
au courant of developments in scientific problems, 
methods and results to be able to form a judgment of 
his own Through many years of hard work he has 
devoted himself to this object with great intelligence 
and no less great determination, and done us all, and 
science a service for which we cannot be too grateful 
It was necessary for him to secure the co-operation of 
successful scientific writers and induce them to say 
what they had to say in a form as far as possible intel- 
ligible to non-speaalists He has often told me of the 
fights he had in pursuing this object, the difficulties of 
which he once described to me in the following nddle 
Question "What is a scientific author? Answer A 
cross between a mimosa and a porcupine 1 Berliner’s 
achievement would have been impossible but for the 
peculiar intensity of his longmg for a clear, compre- 

Do not be angry w th me for th s tnd sermon, mv 
senous mmded man eojovt a good laugh now A 



hensivc view of the largest possible area of saentific 
country This feeling also drove him to produce a 
text-book of physics, the fruit of many years of strenuous 
work, of which a medical student said to me the other 
day "I don't know how I should ever have got a clear 
idea of the principles of modem physics in the time at 
my disposal without this book " 

Berliner’s fight for clarify and comprehensiveness of 
outlook has done a great deal to Bring the problems, 
methods and results of science home to many people’s 
minds The saentific life of our time is simpl) incon- 
ceivable without his paper It is just as important to 
make knowledge live and to keep it alive as to solve 
specific problems We arc all conscious of what we 
owe to Arnold Berliner 

Popper-Lytikctus was more than a brilliant engineer 
and writer He was one of the few outstanding per- 
sonalities who embody the consacncc of a generation 
He has drummed it into us that soaecy is responsible 
for the fate of ever) individual and shown us a way to 
translate the consequent obhganon of the community 
,mto fact The community or state was no fetish to 
him, he based ns right to demand sacrifices of the 
individual entirely on its duty to give the individual 
personality a chance of harmonious development 

Obituary of the Surgeon, M Katzcnstem 

Dunng the eighteen jears I spent m Berlin I had few 
dose friends, and the doses t was Professor Katzen- 
stein For more than ten ) ears I spent m> leisure hours 
•hrnnq, 'ho. vrnwmv; m nurhe, him., mtirshj 'in. hie, 
delightful yacht There W'c confided our experiences, 


ambitions, emotions to each other. Wc both felt that 
this friendship was not only a blessing because each 
understood die other, was enriched by him, and found 
in him that responsive echo so essential to. anybody who 
is truly alive ; it also helped to make both of us more 
independent of external experience, to objectivise it 
more easily. 

I was a free man, bound neither by many duties nor 
by harassing responsibilities; my friend, on the con- 
trary, was never free from the grip of urgent duties and 
anxious fears for the fate of those in peril. If, ns was 
invariably the case, he had performed some dangerous 
operations in the morning, he would ring up on the 
telephone, immediately before we got into the boat, to 
enquire after the condition of the patients about whom 
■ he was worried ; I could sec how deeply concerned he 
was for the lives entrusted to his care. It was marvellous 
that this shackled outward existence did not clip the 
wings t)f his soul ; his imagination and his sense ol 
humour were irrepressible. He never became the 
typical conscientious North-German, whom the Italian! 
in the days of their freedom used to call bestia seriosa 
He was sensitive as a youth to the tonic beauty of the 
lakes and woods of Brandenburg, and as he sailed the 
boat with an expert hand through these beloved and 
familiar surroundings he opened the secret treasure- 
chamber of his heart to me— he spoke of his experiments, 
scientific ideas, and ambitions. How he found time anc 
energy for them was always a mystery to me; but tht 
passion for scientific enquiry is not to be crushed b> 
any burdens. The man who is possessed with it perishe: 
sooner than it does. r 

There were two types of problems that engaged hi 
attention. The first forced itsMf on him out of the 



necessities of his practice Thus he was always thinking 
out new ways of inducing healthy muscles to take the 
place of lost ones, by ingenious transplantanon of 
tendons He found this remarkably easy, as he possessed 
an uncommonly strong spatial imagination and a 
remarkably sure feeling for mechanism How happy 
he was when he had succeeded in making somebody fit 
for normal life by putting right the muscular system of 
his face, foot or arm* And the same when he avoided 
an operation, even in cases which had been sent to him 
by physicians for surgical treatment (in cases of gastric 
ulcer by neutralising the pepsin) He also set great 
store by the treatment of peritonitis by an anti-toxic 
coil-serum which he discovered, and rejoiced in the 
successes he achieved with it In talking of it he often 
lamented the flvt that this method of treatment was not 
endorsed by his colleagues 
The second group of problems had to do with the 
common concepnon of an antagonism between different 
sorts of tissue He believed that he was here on the track 
of a general biological principle of widest application, 
whose implications he followed out with admirable 
boldness and persistence Starting out from this basic 
nonon he discovered that osteomyelon and periosteum 
prevent each other’s growth if they are not separated 
from each other by bone In this way he succeeded m 
explaining hitherto inexplicable eases of wounds fail- 
ing to heal, and m bringing about a cure 
This genera! notion of the antagonism of the tissues, 
especially of epithelium and connecm e tissue, was the 
subject to which he devoted lus scientific energies, 
especially in the last ten years of lus life Experiments 
on animals and a systematic mv esnganon of the growth 
of tissues in a nutrient fluid were earned out side by 


side. How thankful he was, with his hands tied as they 
were by his duties, to have found such an admirable 
and infinitely enthusiastic fellow-worker in Friculeni 
Knake! He succeeded in securing wonderful results 
bearing on the factors which favour the growth of 
epithelium at the expense of that of connective tissue, 
results which may well be of derisive importance for the 
study of cancer. He also h*ad the pleasure of inspiring 
his own son to become his intelligent and independent 
fellow-worker, and of exciting the warm interest 
and co-operation of Sauerbruch just in the last years 
of his life, so that he was able to die with the consoling 
diought that his life's work would not perish but 
would be vigorously^ continued on the lines he had 
laid down. 

I for my part am grateful to fate for having given me 
this man, with his inexhaustible goodness and high 
creative gifts, for a friend. 

Congratulations to Dr. Solj 

I am delighted to be able to offer you, Dr. Solf, 
the heartiest congratulations, the congratulations of 
Lessing College of which you have become an 
indispensable pillar, and the congratulations of all who 
are convinced of the need for close contact between 
science and art and the public which is hungry for 
spiritual nourishment. " ' 

You have not hesitated to apply y0U r energies to a 
held where there are no laurels to be won, but quiet 
loyal work to be done in the interests of the general 
standard of intellectual and spiritual life, which is in 
peculiar danger to-day owing to a variety of circum- 
stances. Exaggerated respect for athletics, an excess of 


coarse impressions which the complication of life through 
the technical discoveries of recent >cars has brought 
with it, the increased seventy of the struggle for 
existence due to the economic crisis, the brutalisation of 
political life — all these factors are hostile to the npening 
of the character and the desire for real culture, and 
stamp our age as barbarous, matenahsne and superficial 
Specialisation m every sphere of intellectual work 
is producing an ever-widening gulf between the 
intellectual worker and the non-speaahst, which 
makes it more difficult for the life of the nanon to be 
fertilised and ennehed by the achievements of art and 

But contact between the intellectual and the masses 
must not be lost It is necessary for die elevation of 
society and no less so for renewing the strength of the 
intellectual worker, for the flower of science docs not 
grow m the desert For this reason you, Herr SoI£ 
have devoted a portion of your energies to Lessing 
College, and vve are grateful to )ou for doing so 
And we wish you further success and happiness in your 
work for this noble cause 

Of Wealth 

I am absolutely convmced that no wealth in the 
world can help humanity forward, even in the hands 
of the most devoted worker in this cause The example, 
of great and pure characters is the only thing that can 
produce fine ideas and noble deeds Monfc) onlv 
appeals to selfishness and always tempts its owners 
irresistibly to abuse it 

Ola vtmegeut Moots, Jtsra vt Gasv&n aimed 

with the money-bags of Carnegie 1 


Education and Educators 
A letter 

Dear Miss 

I have read about sixteen pages of your manuscript 
and it made me— smile. It is clever, well observed, 
honest, it stands on its own feet up to a point, and yet 
it is so typically feminine, by which I mean derivative 
and vitiated by personal rancour. I suffered exactly 
the same treatment at the hands of my teachers, who 
disliked me for my independence and passed me over 
when they wanted assistants (I must admit that I was 
somewhat less of a model student than you). But it 
would not have been worth my while to write anything 
about my school life, still less would I have liked to be 
responsible for anyone’s printing or actually reading it. 
Besides, one always cuts a poor figure if one complains 
about o tlicrs who arc struggling for their place in the 
sun too after their own fashion. 

Therefore pocket your temperament and keep your 
manuscript for your sons and daughters, in order that 
they may derive consolation from it and — not give a 
damn for what their teachers tell them or think of them. 

Incidentally I am only coming to Princeton to 
research, not to teach. There is too much education 
altogether, especially in American schools. The only 
rational way of educating is to be an example— of what 
~to avoid, if one can't be the other sort. 

With best wishes. 

To the Schoolchildren of Japan 

In sending this greeting to you Japanese school- 
children, I can lay claim to a special right to do so, ' For " 


I have m>self visited your beautiful country, $e< 
cities and houses, its mountains and woods, and in 
Japanese boys who had learnt from them to love 
country A big fat book full of coloured drawjni 
Japanese children lies always on my table 

If you get my message of greeting from 3II 
distance, bethink y ou that ours is the first age in hr 
to bring about friendly and understanding intera 
between people of different countries , in former t 
nations passed their lives in mutual ignorance, an 
fact hated or feared one another May* the spin 
brotherly understanding gain ground more and r 
among them With this in mind I, an old man, f 
you Japanese schoolchildren from afar and hope 
your generation may some day put mine to sh ame 

Teachers and Pupils 
An address to children 

(The principal art of the teacher is to awaken the joy in creation 
ana knowledge ) 

My dear Children, 

I rejoice to sec you before me to-day, happy youth 
of a sunny and fortunate land 

Bear m mind that the wonderful things you learn 
m your schools arc die work of many generations, 
produced by cndiusiasuc effort and infinite labour in 
everv country of the world All dm is put into your 
hands as your inheritance in order diat you may receive 
it, honour it, add to it, and one day faithfully hand it on 
to your children Thus do we mortals achieve immor- 
.tcvUy jr ahr ptatroan-W *shugv* .Vihtsh wr -in 




If you always keep that in’ mind you will find a 
meaning in life and work and acquire the right attitude 
towards other nations and ages. 

1 Paradise Lost 

As late as the seventeenth century the savants and 
artists of all Europe were so closely united by the bond 
of a common ideal that co-operation between them was 
scarcely affected by political events. This unity was 
further strengthened by the general use of the Latin 

To-day we look back at this state of affairs as at a 
dost paradise. The passions of nationalism have des- 
troyed this community of the intellect, and the Latin 
language, which once united the whole world, is dead. 
The men of learning have become die chief mouthpieces 
of national tradition and lost their sense of an intellectual 

Nowadays wc arc faced widi the curious fact that 
the politicians, ffjc practical men of affairs, have become 
the exponents of international ideas. If is diey who 
have created the League of Nations. 

Religion aitd Science 

Ever) thing that the human race has done and thought 
is concerned with the satisfaction of felt needs and the 
assuagement of pain. One has to keep this constantly 
in mind if one wishes to understand spiritual move- 
ments and their development. Feeling and desire are 
the motive forces behind all human endeavour and 
human creation, in however exalted a guise the latter 
may present itself to us. Now what are the feelings 


and needs that have led men to religious thought and 
belief in the widest sense of the vv ords > A htde con- 
sideranon wall suffice to show us that die most varying 
emotions preside over the birth of religious thought 
and experience QWith primitive man it is abov<r all 
fear that evokes religious notions — fear of hunger, Wild 
beasts, sickness, death Since at this stagt of existence 
understanding of causal connexions is usually poorly 
developed, the human mind creates for itself more or 
less analogous beings on whose wills and actions these 
fearful happenings depend One’s object now is to 
secure die favour of these beings by carr) mg out actions 
and offering sacrifices which, according to the tradition 
handed down from generation to generation, propitiate 
them or make them well disposed towards a mortal 
I am speaking now of the religion of fear This, though 
not created, is in an important degree stabilised by die 
formation of a special pnestly caste which sets up as a 
mediator between the people and the beings diey fear, 
and erects a hegemony on dm basis In many cases 
the leader or ruler whose position depends on other 
factors, or a privileged class, combines pnestly functions 
with its secular authority in order to make the latter 
more secure, or the political rulers and die pnesdy 
caste make common cause in their own interests ) 

The social feelings are another source of the crystal- 
lisation of religion Fathers and modiers-and the leaders 
of larger human communities are mortal and fallible 
The desire for guidance, love and support prompts 
men to form the social or moral conception of God. 
Tim is the God of Providence who protects, disposes, 
rewards and punishes, the God who, according to the 
width ot the "believer's outlook, loves and cherishes the 
life of the mbe or of the human race, or cv en life as 


such, the comforter m sorrow and unsatisfied longing, 
who preserves the souls of the dead This is the social 
or moral conception of God 
TheTewish scriptures admirably illustrate the develop - 
ment from the~ rekgion of fea r t o moral religion, which 
£T continued in the New Testa ment The religions of 
all civilised peoples , es pedallytKe peoples of the Orient , 
are pnmanly moral religion s The development from 
a religion of tear to 'moral religion is a great step m a 
nation’s life* That primitive religions are^based entirely 
on fear and the religions of civilised peoples purely on 
morality is a prejudice against which we must be on our 
guard The truth is that they are all intermediate types, 
with this reservanon, that on the higher levels of social i 
hfe the religion of morality predominates 
Common to nil these types is the anthropomorphic 
character of their conception of God Only individuals 
of exceptional endowments and exceptionally high- 
minded communities, as a general rule, get in any real 
sense beyond this level But there is a third state of 
religious experience which belongs to all of them, even 
though it is rarely found m a pure form, and which I 
will call cosmic religious feeling It is very difficult 
to explain this /eeling to any one who is entirely 
without it, especially as there *s no anthropomorphic 
concepuon of God corresponding to it 
The individual feels the nothingness of human 
desires and aims and the sublimity and marvellous order 
which reveal themselves both m nature and in the world 
of thought He looks upon individual exi stence as a 
son of prison and wants to experience the univer se ~as 
^Singl e . signi fica nt whol e The beginnings ot cosmic 
religious feeling already appear m earlier stages of 
development, e g , in many of the Psalms of David and 


in some of the Prophets Buddhism, as we have leamt 
from the wonderful writings of Schopenhauer especi- 
ally, contains a much stronger clement of it. 

The religious geniuses of all ages have been dis- 
tinguished by this kind of religious feeling, which knows 
no dogma and no God conceived m man’s image; so 
that there can be no church whose central teachings are 
f based on* it. Hence it is precisely among the heretics 
of every age that we find men who were filled with the 
highest kind of religious feeling and were m many 
cases regarded by their contemporaries as atheists, 
sometimes also as saints. Looked at in this light, men 
like Democntus, Francis of Assisi, and Spinoza arc 
closely akin to one another. 

How can cosmic religious feeling be communicated 
from one person to another, if it can give rise to no ' 
definite notion of a God and no theology i In my view, 
it is the most important function of art and science to 
awaken this feeling and keep it alive in those who arc 
capable of it 

£Wc thus arrive at a conception of the relation of 
science to religion very different from the usual x>ne 
When one view's the matter historicall y one is inclined 
to look upon science and 'lehgion *as irreconcilable 
antagonists, and for a very obvious reason The man 
who is thoroughly convinced of the universal operation 
of the law of causation cannot for a moment en terrain 
the idea of a being who interferes m the course of events 
— that is, if he takes the hypothesis of causality really 
seriously He has no use for the religion of fear and 
equally little for social or moral religion A God who 
rewards and punishes is m conceivable to him for die 
simple reason that a man’s actions are determined by 
necessity, external and internal, so that m God’s eyes 


lie cannot be responsible, any more than an inanimate 
object is responsible for the motions it goes through 
Hence science has been charged with undermining 
morality, but the charge is unjust A man’s ethical 
behaviour should be based effectually on sympathy, 
education, and social ties , no religious basis is necessary 
Man would indeed be in a poor way if he had to be 
restrained by fear and pumshment and hope of reward 
after death y 

It is therefore easy to see why the churches have 
always fought science and persecuted its devotees On 
the other hand I maintain that cosmic religious feeling 
is the strongest and noblest incitement to scientific 
research Only those who realise the immense efforts 
and, above all, the devotion which pioneer work in 
theoretical science demands, can grasp the strength of 
the emotion out of which alone such work, remote as 
it is from the immediate realities of life, can issue 
What a deep conviction of the rationality of the 
universe and what a yearning to understand, were it 
hut a feeble reflecuon of the mind revealed m this 1 
world, Kepler and Newton must have had to enable 
them to spend years of solitary' labour in disentangling^ 
the principles of celestial mechanics’ Those whose 
acquaintance with scientific research is denved chiefly 
from its practical results easily develop a completely 
false notion of the mentality of che men who, sur- 
rounded by a sceptical world, have shown the way to 
those like-minded with themselves, scattered through 
the earth and the centuries £ Onl\ one who has devoted 
his hfc to similar ends can have a vivid realisation of 
what has inspired these men and given them the 
strength to remain true to dieir purpose in spite of 
countless failures It is cosmic religious feeling that 



gives a man strength of this son A contemporary lias 
said, not unjust!) , that in this materialistic age of ours 
the serious scientific workers are the only profoundly 
religious people } - 

The Keitgtcusness of Science 

You will hardly find one among the profounder sort 
of scientific minds without a peculiar religious feeling 
of his own But it is different from the religion ofithe 
naive man For the latter God is a being from whose 
care one hopes to benefit and whose punishment one 
fears, a sublimation of a feeling similar to that of a 
child for -its father, a being to whom one stands to some 
extent m a personal relation, however deeply it may be 
tinged with awe 

But the scientist is possessed by the sense of universal 
causation The future, to him, is every whit as necessary 
and determined as the past There is nothing divin e 
about morality, it is a purely human affair His religio us 
feeling takes die form of a rapturous amazement at the 
harmony of natural law , which reveals an intelligen ce 
oflsuch superio rity that, compared with if, all the 
s ystematic thinking and acting of hum an beings is an 
utterly insignificant reflection" Ibis feeling is the 
guiding principle of his life and work, m so far as he 
succeeds in keeping himself from the shackles of selfish 
desire It is beyond quesuon closely akin to chat which 
has possessed die religious geniuses of all ages 

The Plight of Science 

The German-speaking countries are menaced by a 
danger to which those in the know are m duty bound 


has been paid for by the martyr’s blood of pure 
'rear men, for whose sake Italy is soil loved and 
bnced to-day . 

be it from me to argue with you about what' 
ids on human liberty may be justified by reasons 
ate But the pursuit of scientific truth, detached 
i the pracncal interests of everyday life, ought to 
Teatcd as sacred by every government and it is 
ne highest interests of all that honest servants of 
\ should be left in peace Tins is also undoubtedly 
t c interests of the Italian state and its prestige in the 
jt of the world 

loping that my request will not fall on deaf ears, 
(a, etc 


To be called to account publicly for everything one 
k said, even in jest, an excess of high spirits or momen- 
ry anger, fatal as it must be in the end, is yet up to a 
nnt reasonable and natural But to be called to 
fount publicly for what others have said in one’s 
tme, when one cannot defend oneself, is indeed a 
d predicament ‘ But who suffers such a dreadful 
'tje> >ou will ask Well, everyone who is of 
'ifraent interest to the public to be pursued bj mter- 
lewers You smile incredulously, but I have had 
knrj of direct experience and Mill tell you about 

( Imagine the following situation One momintr a 

reporter comes to - ’ - - e 

:q tell lum someth 
you no doubt feel 

m a mendly way 
mg about jour friend N At first 
something approaching indignation 



icd to express the 

at such a proposal But of the American nation, 
is no escape If youu'gh sense of responsibility, w»* 
writes “I asked elf to the sphere of politics For 
about him Bio-operation of the great country 
This'in ltselfates in the business of regulating 
conclusions, all efforts directed towards tins 

- nound to remain more or less ineffectual 
? I thank you most heartily for this 
reception and, in particular, the men of leamrn 
this country for the cordial and friendly W'- 1 
have received from them I shall always look * 
these two months with pleasure and gratitude 

The Unnersity Course at Davos 

Senatores bom vm, senatus autem bestia So a r 
of mine, a Swiss professor, once wrote in his irntal 
way to a university faculty which had annoyed 1 
Communities tend to be less guided than 
by conscience and a sense of responsibility What 
fruitful source of suffering to mankind this fact i 
It is the cause of wars and every kind of oppressio 
which fill the earth with pain, sighs, and bitterness 

And yet notlung truly valuable can be achieved 
except by the unselfish co-openmon of many indi 1 
viduals Hence the man of good will is never happict 
than when some communal enterprise is afoot and \ 
launched at die cost of heavy sacrifices, with the singl 
object of promoting life and culture ! 

Such pure joy was nunc when I heard about th 1 
university courses at Davos A work of rescue is bcuu 
earned out there, with intelligence and a wise modcra 
non, which is based on a grave need, diough it may no 


of infancy May it prosper, enriching the 
of numbers of admirable human beings and resa, 
many from the poverty 'of sanatorium life 1 Vih 

Congratulations to a Critic ' 

To see with one’s own eyes, to feel and judge wicf^ 
succumbing to the suggestive power of thefashioi 
the day, to be able to express what one has seen 
in a snapp) sentence or even in a cunningly wro 
word — is that not glonous » Is it not a proper sill 
for congratulation » „i 

Greeting to G Bernard Shaw 
There arc few enough people with sufficient mdepel 
dencc to see the weaknesses and follies of their conten 
poranes and remain themselves untouched b) >’ 
And these isolated few usually soon lose their zeil * 
putting things to rights when they have come face 
face with human obduracy Only to a arty minority 
it given to fascinate their generation by subtle * 
and grace and to hold the mirror up to it by the 
personal agency of art To-day I salute with 
emotion die supreme master of this method, who 1 
delighted — and educated — us all 

* Some Notes on my American Impressions 
I must redeem my promise to say somednng 
my impressions of this country That is not altogethj 
easy for me For it iS not easy to take up the atmucV 
of an impartial observer when one is received witf 
such kindness and undeserved respect as I have been ^ 
America First of all let me say something on this heaf 
36 < 


cafe cult of individual personalities is always, in my 
JJj unjustified. To be sure, nature 'distributes her 
n i Variously among her children. But there are plenty 
b o'e well-endowed ones too, thank God, and I am 

J 'Ay Convinced that most of them live quiet, un- 

. .. . .r ■ ] L „ A 

jT&tled lives. It strikes me as unfair, and even in bad 
p, to select a few of them for boundless admiration, 
j/jbuting superhuman powers of mind and character 
gLfrhem. This has been my fate, and the contrast 
ir$rc£n the popular estimate of my • powers and 
Moments and the reality is simply grotesque. The 
A is aousness of this extraordinary state of affairs would 
^..(unbearable but for one great Consoling thought: it is 
nWelpome symptom in an age which is commonly 
Jenonmced as materialistic! that it makes heroes of men 

I irhose ambitions lie wholely in the intellectual and 
not al sphere. This proves that knowledge and justice 
ire tanked above wealth and power by a large section 
of the human race. My experience teaches me that 
this.* idealistic budook is particularly prevalent in 
America, which is usually decried as a particularly 
materialistic country. After this digression I come to 
; m y\ proper theme, in the hope that no more weight 
Mtlchcd to my modest remarks than they 

"What first strikes the visitor with 'smarement is the 
apriority of this country in matters of technics and 

nation. Objects of everyday me are more solid 
m Europe homes infinitely more convenient in 

its natural 

-t“ E r Dri r?r t , on ^ - «*«- 

Revoked the maULX^ntrftS 



devices and methods of work The opposite extreme 
is illustrated by over-populated China or India, Where 
the low price of labour has stood in the way flf the 
development of machinery Europe is half-way between 
the two Once the machine is sufficiently highly 
developed it becomes cheaper in the end thanl the 
cheapest labour. Let the Fascists in Europe, who desire 
on narrow-minded political grounds to see their qwn 
particular countries more densely populated, take Heed 
of this The anxious care with which the Uiuted S/mccs 
keep out foreign goods by means of prohibitive nW 1 ® 
certainly contrasts oddly with this non on . Bijh an 

innocent visitor must not be expected to rack his bp 1115 
too much, and, when all is said and done, it lsjnot 
absolutely certain that every question admits c£f 3 
rational answer j 

The second thing that strikes a visitor is the joyf ous ’ 
positive attitude to life' The smile on the faces ofj the 
.people w photographs is symbolical of one off die 
American’s greatest assets He is fnendly, confioiCnt, 
optimistic, and — without envy The European fijnds 
intercourse with Americans easy and agreeable ] 
Compared with the American, the European is rr/otf 
critical, more self-consaous, less good-hearted <and 
helpful, more isolated, more fastidious m his aml.W’ 
ments and his reading, generally more or less ojf 4 
pessinust / 

Great importance attaches to the material cormforts 
of life, and peace, freedom from care, security arc all 
sacrificed to diem The American lives for ambition, 
the future, more than the European Life for Mia I s 
always becoming, never being In this respect jbe is 
even further removed from the Russian andS the 
Asiatic than the European is But there is another 


respect in which he resembles the Asiatic more than the 
EurotP ean does he is less of an individualist than the 
European — that is, from the psychological, not the 
economic, point of view ^ m (l )t 

jyjjore emphasis is laid on the we than the 1 . 
As .1 natural corollary of tins, custom and convention 
are / very powerful, and there is much more uni- 
formity both in outlook on life and in moral and. 
restuetic ideas among Americans than among Euro- 
peans This fact is chiefly responsible for America's 
economic superiority over Europe Co-operation and 
the Vhvision of labour are earned through more easily 
and! with less friction than in Europe, whether in the 
factory or the university or in private good works 
This social sense may be partly due to the English 

In apparent contradiction to this stands the fact that the 
actmues of the state are comparatively restricted as 
compared with Europe The European is surprised to 
find the telegraph, the telephone, the railways and the 
schools predominantly in private hands The more 
social attitude of the individual, which I mentioned just 
now, makes this possible here Another consequence 
of this attitude is that the extremely unequal distri- 
bution of property leads to no intolerable hardships 
The social conscience of the rich man is much more 
higlfly developed than in Europe He considers himself 
obliged as a matter of course to place a large portion 
v °, j wealth, ^ °^ en °f lus own energies too. at 

rWltP 0521 comraunit y* and public opinion, 
that ^-powerful iorce, impenously demands it of him 
Hence the most important cultural fimedons can be left 
to private enterprise and the part played by* e s a * 
m dm country is, comply, a very reacted o“ 



The prestige of government has undoubtedly^ been 
lowered considerably by the Prohibition laws.Pj fur 
nothing is more destructive of respect for die gopvero- 
ment and the law of the land than passing laws wyHch 
cannot be enforced. It is an open secret than tic 
dangerous increase of crime in this country is clclscty 
connected with this. I 

There is also another way in which Prohibition! in 
my opinion, has led to the enfeeblement of the state. 
The public-house is a place which gives people a ch juice 
to exchange views and ideas on public affairs. As ^ 
as I can see, people here have no chance of doin^-lfus, 
the result being that the Press, which is mostly con- 
trolled by definite interests, has 3n excessive influence 
over public opinion. - . 

The over-estimation of money is still greater in this 
country than in Europe, but appears to me to be on the 
decrease. It is at last beginning to be realised that great 
wealth is not necessary for a happy and satisfactory life- 
As regards artistic matters, I have been genuinely 
impressed by the good taste displayed in the modem 
buildings and in articles of common use; on the other, 
hand the visual arts and music have little place in the 
life of the nation as compared with Europe. 

I have a warm admiration for the achievements of 
American institutes of scientific research. We are 
unjust in attempting to ascribe the increasing superiority 
of American research-work excluiivcly to superior* 
wealth; zeal, patience, a spirit of comradeship and a _ 
talent for co-operation play an important part in its 
successes. One more observation to finish up with. 
The United States are the most powerful technically 
advanced, country in. the world to-day.. Their influence 
on the shaping of international relations is absolutely 


incalculable. But America' is a large country^ and its 
people have so far not shown much interfist in great 
international problems, among which the problem of 
disarmament occupies first place to-day. This must be 
changed, if only in the essential interests of die Ameri- 
cans. The last war has shown that there are no longer 
any barriers between the continents and diat the 
destinies of all countries are closely interwoven. The 
people of this country must realise that they have a 
great responsibility in the sphere of international 
politics. The part of passive spectator is unworthy of 
tills country and is bound in the end to lead to disaster 
all round. 

Reply to the Women of America 

An American Women’s League felt called upon to protest 
against Einstein’s visit to their country. They received the fol- 
lowing answer. 

Never yet have I experienced from the fair sex such 
energetic rejection of all advances; or if I have, never 
from so many at once. 

But are they not quite nght, these watchful citizen- 
esses ! "Why should one open one’s doors to a person 
who devours hard-boiled capitalists with as much appe- 
tite and gusto as the Cretan Minotaur in days gone by 
devoured luscious Greek maidens, and on top of that 
is low-down enough to reject every sort of war, except 
the unavoidable war with one’s own wife ? Therefore 
give heed to your clever and patriotic wconen-f&Hc 
and remember that the Capitol of mighty Rome was 
once saved by the cackling of its faithful geese 


Part II 




r T'HE importance of securing international peace was 
* recognised by the really great men of former 
generations But the technical advances of our times 
have turned this ethical postulate into a matter of life 
and death for civilised mankind to-day, and made the 
taking of an active part m the solution of the problem 
of peace a moral duty which no conscientious man 
man can shirk 

One has to reahse that the powerful industrial groups 
concerned in the manufacture of arms are doing their 
best in all countries to prevent the peaceful settlement 
of ^international disputes, and that rulers can only 
achieve this great end if they arc sure of the vigorous 
support of the majority of their peoples In these days 
ot democrauc government the fate of die nations hangs 
on themselves, each individual must always bear that 
m mind 

The Pacifist Problem 
Ladies and Gentlemen, 

%Cr ^' th* 5 opportunity of saying a few 

rn„ V° U about thc problem of pacificism The 
C ^ cnts m t bc last few years has once more 
.3",“ Kow Iwk we ate justified m leaving the 
to I!, aS1UB< armam cnts and against the war sprat 
D n'„f' trnmcms On the other hand, the formation 
g rgamsanons with a large membership can of 
4 $ 


itself bring us very little nearer to our goal. In 
opinion, the best method in this case is the violent) 
of conscientious objection, with the aid of organise* 
for giving moral and material support to the courage 
conscientious objectors in cadi country. In this way 
may succeed in malting the problem of pacificism 
acute one, a real struggle which attracts forceful naru 
It is an illegal struggle, but a struggle for people’s i 
rights against their governments w so far as the In! 
demand criminal acts of the arizen. 

Many who think themselves good pacifists will, 
at this out-and-out pacifism, on patriotic groun 
Such people are not to be relied on in the hour ofai 
as the world war amply proved. 

I am most grateful to you for according me 
opportunity to give you my views in person. 

Address to the Students' Disarmament Meeting 

Preceding generations have presented us, in a high] 
developed saence and mechanical knowledge, with 
most valuable gift which carries with it possibilities ( 
making our life free and beaurifid such as no prewot 
generation has enjoyed. But this gift also brings withj 
dangers to our existence as great as any that have eve 
threatened it. 

The destiny of dvilised humanity depends more thai 
ever on the moral forces it is capable' of generating 
Hence the task that confronts our age is certainly nc 
easier than the tasks our immediate predecessor 
successfully performed. 

The foodstuffs and other goods which the world 
needs can be produced in far fewer hours of work than 
formerly. But this has made the problem of the division 


jon, from Jesus Christ to Goethe and Kani Is it 
"mficant that such men have been umversaUy 
]t d as leaders, in spite of the fact that their efforts 
uld the course of human affairs were attended 
but small success? 

m convinced that the great men, those whose 
cements, even though in a restricted sphere, set 
above their fellows, arc animated to an over- 
turn g extent by the same ideals But they have 
influence on die course of pohncal events It 
st looks as if this domain, on which die fate of 
>ns depends, had inevitably to be given over to 
:ncc and irresponsibility 

ihtical leaders or governments owe their position 
ly to force and pardy to popular election They 
tot be regarded as representative of the best elements, 
•ally and intellectually, m dieir respective nations 
intellectual elite have no direct influence on die 
ary of nations in these days, their lack of cohesion 
yents them from taking a direct part in die solution 
contemporary problems Don’t you dunk diat a 
nge might be brought about m dus respect by a 
i association of people whose work and achieve- 
nts up to date constitute a guarantee of their ability 
1 punty of aim? This international association, 
lose members would need to keep m touch with 
h other by a constant interchange of opinions, might, 
defining its attitude in the Press— responsibility 
■vays resting with the signatories on any given 
casion — acquire a considerable and salutary moral 
flncnrr &W sademear peitaal qusttans 
ich an assoaanon would, of course, be a prey to all 
cills which so often lead to degeneranon in learned 
►ciedcs, dangers which are inseparably bound up with 


the irtperfecoon of human nature But should not an 
effort in tins direction be risked m spite of this’ I look 
upon the attempt as nothing less than an imperative 

If an intellectual association of standing, such as I 
have described, could be formed, it would no doubt 
ha\c to try to mobilise the religious organisations for 
the fight against war It would give countenance to 
many whose good intentions are paralysed to-day by a 
melancholy resignation Fmilly, I believe that an 
association formed of persons such as I have described, 
each highly esteemed in lus own hue, would be just 
the dung ro give valuable moral support to those 
elements in the League of Nations which arc rcall) 
working for the great object for which that institution 

I had rather put diese proposals to you than to anyone 
else in the world because you arc least of all men the 
dupe of y our desires and because y our critical judgment 
is supported by a most earnest sense of responsibility 

Compulsory Service 
From a letter 

Instead of permission being given to Germany to 
introduce compulsory service it ought to be taken away 
from everybody else m future none but mercenary 
armies should be permitted, die size and equipment of 
which should be discussed at Geneva This would be 
better for France dian to base to permit compulsory 
service in Germany The fatal psvdiological effect of 
the military education of die people and the violation 
of the individual s rights wlucii it involves would dius 
be avoided 



' Moreover, it would be much easier for two countries 
which had agreed to compulsory arbitration for the 
settlement of all disputes arising out of their mutual 
relations to combine their military establishments of 
mercenaries, into a single organisation with a mixed 
staff. This would mean a financial relief and increased 
security for both of them. Such a process of amal- 
gamation might extend to larger and larger com- 
binations, and finally lead to an “international police,” 
which would be bound gradually to degenerate as 
international security increased. 

Will you discuss this proposal with our friends by 
way of setting the ball rolling > Of course I do not in 
the least insist on this particular proposal. But I do think 
it essential that we should come forward with a positive 
programme; a merely negative policy is unlikely to 
produce any practical results. 

Germany and France 

Mutual trust and co-operation between France and 
Germany can only come about if the French demand for 
security against military attack is satisfied. But should 
France frame demands in accordance with this, such a 
step would certainly be taken very ill in Germany. 

A procedure something like the following seems, 
however, to be possible. Let the German government 
L °' Vn W1 ^ propose to the French that they 
should jointly make representations to the League of 
Nations that it should suggest to all member states to 
bind themselves to the following : — 

to To submit to ever)- decision of the international 
court of arbitration. 

•fc) To proceed with all its economic and military 


force, in concert with the other members of the League, 
against any state which breaks the peace or resists ai) 
international decision made in the interests of world 


Systematic disarmament within a short period. This 
is only possible in combination with the guarantee of 
all for the security of each separate nation, based on a 
permanent court of arbitration independent of govern- 
ments. i 

Unconditional obligation of all countries not merely 
to accept the decisions of the "court of arbitration but 
also to give effect to them. 

Separate courts of arbitration for Europe with 
Africa, America, and Asia (Australia to be apportioned . 
to one of these). A joint court of arbitration for 
questions involving issues that cannot be setded within 
the limits of any one of these three regions. 

The International of Science 

At a sitting of the Academy during die War, at die 
rime when national and political infatuation had 
readied its height, Emil Fischer spoke die following 
emphatic words : — “It’s no use. Gentlemen, saence is and 
"'•remains international.” The really great saentists have 
always known this and felt it passionately, even though 
m times of political confusion.they may have remained 
isolated among didr colleagues of inferior calibre. In 
every camp during the War this mass of voters betrayed 
dicir sacred rrusr. The international sodccy of the 
academies was broken up. Congresses were and still 


aie held from which colleagues from ex-enemy coun- 
tries are excluded Political considerations, advanced 
with much solemnity, pre /ent the triumph of purely 
objective ways of thinking without which our great 
aims must necessarily be frustrated 
What can. right-minded. people, people who are proof 
against the emotional temptations oftnc moment, do to 
repair the damage? With the majority of intellectual 
workers still so excited, truly international congresses 
on the grand scale cannot yet be held The psychological 
obstacles to the restoration of the international associ- 
ations of scientific workers are still too formidable to 
be overcome by the minority whose ideas and feelings 
are of a more comprehensive kind These last can aid 
in the great work of restoring the international societies 
to health by keeping in close touch with like-minded 
people all over the world, and resolutely championing 
the international cause m their own spheres Success 
on a large scale will take time, but it will undoubtedly 
come 1 cannot let this opportunity pass without paying 
a tribute to the way m which the desire to preserve the 
confraternity of the intellect has remained alive through 
all these difficult years m the breasts of a large number’ 
of our English colleagues especially 
The disposition of the individual is everywhere better 
than the official pronouncements Right-minded people 
should bear this in mind and not allow themselves to be 
misled and get angry senafores tom vm, senator autern 

If I am full of confident hope concerning the progress 
of international organisation in general, that feeling is 
based not so much on my confidence m the intelligence 
and high-mindcdness of my fellows, but rather on the 
irresistible pressure of economic de\ clopments And 


since these depend largely on the work even of re- 
actionary scientists, they too will help to create the 
international organisation against their wills. 

The Institute for Intellectual Co-operation 

During this year the leading politicians of Europe 
have for die first time drawn the logical conclusion 
from die truth that our porridn of the globe can only 
regain its prosperity if the underground struggle 
between the traditional political units ceases. The 
pohacal organisation of Europe must be strengthened, 
and a gradual attempt made to abolish tariff barriers. 
Tlus great end cannot be achieved by treaties alone. 
People’s minds must, above all, be prepared for it. 
We must try gradually to awaken in them a sense of 
solidarity which does not, as hitherto, stop at frontiers. 
It is with this m mind that die League of Nations has 
created the Commission de co-operation intellectuelle. 
This commission is to be an absolutely international 
and entirely non-pohncal authority, whose business it is 
,to put the intellectuals of all the nations, who were 
isolated by the war, inro rouch with each other. It is a 
difficult task; for it has, alas, to be admitted that — at 
least in the countries with which I am most closely 
acquainted — the artists and men of learning are governed 
bymarrowly nationalist feelings to a far greater extent 
dian the men of affairs 

Hitherto this commission has met mice a year. To 
make its efforts more effective, the French government 
has decided to create and maintain a permanent Institute 
for intellectual co-operation, which is just now to be 
opened If is a generous act on the part of the French 
nation and deserves the thanks of all 


It is an easy and grateful task to rejoice and praise 
and say nothing about the things one regrets or dis- 
approves of But honesty alone can help our work 
forward, so I will not shrink from combining criticism 
with this greeting to the new -bom child 
1 ha\c daily occasion for observing that the greatest 
obstacle which the work of our commission his to 
encounter is the lack of confidence in jts political 
impartiality Everything must be done to strengthen 
that confidence and everything avoided that might 
harm it 

When, therefore, the French government sets up and 
maintains an Institute out of public funds in Pans as a 
permanent organ of die Commission, with a Frenchman 
as its Director, the outside observer can hardly avoid 
the impression that French influence predominates in 
the Commission This impression is further strength- 
ened by the fact that a Frenchman has also been chairman 
of the Comnussion itself so far Although the indi- 
viduals m question are men of die highest reputation, 
liked and respected everywhere, nevertheless the im- 
pression remains 

Dm ct salvavt atiunam meant I hope with all my * 
heart that the new Institute b\ constant interacnon with 
the Commission will succeed m promoting their 
common ends and wanning the confidence and recog- 
nition of intellectual workers all o\ er the world 



A Farewell 

A letter to the German Secretary of the League 
of Nations 

Dear Herr Dufour-Feronce, 

Your kind letter must not go unanswered, otherwise 
you may get a mistaken notion of my attitude c 
grounds for my resolve to go to Geneva no more are 
as follows — Experience has, unhappdy, taught me m at 
the Commission, taken as a whole, stands for no serious 
determination to make real progress with the task o 
improving international relations It looks to me ar 
more like an embodiment of the principle jit a iqtu 
fen vidcatur The Commission seems to me even worse 
in this respect than the League taken as a whole 
It is precisely because I desire to work with all tny 
imght for the establishment of an international arbitrat- 
ing and regulative authority superior ttr the state, an 
because I have this object so very much at heart, that 
I feel compelled to leave the Commission ^ 

The Commission has given its blessing to the oppres- 
sion of the cultural minorities in all countries by causing 
a National Commission to he set up m each of them 
which is to form the only channel of communication 
between the intellectuals of a country and the Com 
mission It has thereby deliberately abandoned its 
funcuon of giving moral support to the nation 
minorities in their struggle against cultural oppression 
Further, the attitude of the Commission in c 
matter of combating the chauvinistic and militaristic 
tendencies of education in the various countries has 
been so lukewarm that no serious efforts m this funda- 
mentally important sphere can be hoped for from it 


The Commission has invariably failed to give moral 
support to those individuals and associations who have 
thrown themselves without reserve mto the business of 
working for an international order and against the 
military system 

The Commission has never made any attempt to 
resist 'the appointment of members whom it knew to 
stand for tendencies the very reverse of those it is bound 
in duty to foster 

1 will not worry you with any further arguments, 
smee you will understand my resolve well enough from 
these few hints It is not my business to draw up an 
indictment but merely to explain my position If I 
nourished any hope whatever I should act differently — 
of that you may be sure 

TJie Question of Disarmament 

The greatesrobstacle to the success of the disarmament 
plan was the fact that people in general left out of 
account the chief difficulties of the problem Most 
objects are gamed by gradual steps for example, die 
supersession of absolute monarchy by democracy 
Here, however, we are concerned with an objective 
which cannot be reached step by step 

As long as the possibility of war remains, nations will 
insist on being as perfeedy prepared militarily as they 
can, in order to emerge triumphant from the next war 
It will also be impossible to avoid educating the youth 
in warlike traditions and cultivating narrow national 
vanity joined to die glorification of the warlike spirit 
as long as people have to be prepared for occasions when 
such a spirit wdl be needed in the citizens for the pur- 
pose of war To arm is to give one's voice and make 


one’s preparations not for peace but for war. Therefore 
people will not disarm step by step; they will disarm 
at one blow or not at all. 

The accomplishment of such a far-reaching change 
in the life of nations presupposes a might)' moral effort, 
a deliberate departure from deeply ingrained tradition- 
Anyone who is not prepared to make die fate of hr 
country in case of a dispute depend entirely on the 
decisions of an international court. of arbitration and 
to enter mto a treaty to this effect widiout reserve, is 
not really resolved to avoid war. It is a case of all or 

It is undeniable that previous attempts to ensure 
peace have failed through aiming ar inadequate com- 
promises. . 

Disarmament and security are only to be had ui 
combination The one guarantee of security u an 
undertaking b) all nations to give effect to the derisions 
of die international authority. 

We stand, therefore, at the parting of die ways. 
Whether wc find die way of peace or continue along 
the old road of brute force, so unworthy of our avdifa- 
tion, depends on ourselves. On die one side the freedom 
of die individual and die security of society beckon to 
us, on die other slaver)' for die individual and the 
annihilation of our civilisation threaten us. Our fate 
will be according to our deserts. 

The Disarmament Conference of 1932 

May I begin with an article of pobncal faith t It nun 
as follows : — The state is made for man, not man for the 


state And in this Tespect science resembles the state 
These are old sayings, coined by men for whom human 
personality was die highest human good I should shrink 
from repeating them, were it not that they are for ever 
threatening to fall into oblivion, particularly in diese. 
days of organisation and mechanisation I regard it as 
the chief duty of die state to protect the individual and 
give lnm the opportunity to develop into a creative 

That is to say, the state should be our servant and not 
we its slaves The state transgresses this commandment 
when it compels us by force to engage m military and 
war service, the more so since the object and die effect 
of dus slavish service is to kdl people belonging to other 
countries or interfere widi their freedom of develop- 
ment Wc arc only to make such sacrifices to die state 
as will promote the free development of individual 
human beings To any American, all this may be a 
platitude, but not to any European Hence we may 
hope diat the fight against war will find strong support 
among Americans 

And now for the Disa. mament Conference Ought 
one to laugh, weep or hope when one thinks of it? 
Imagine a at} inhabited by fiery -tempered, dishonest 
and quarrelsome citizens The constant danger to life 
there is felt as a serious handicap which makes all 
* healthy development impossible The magistrate desnes 
to remedy this abominable slate of affairs, aldiough all 
counsellors and the rest of the citizens insist on 


ddzeris do not suppress knifing hy legislation, die courts 
and the police, things go on in the old way, of course. 
A definition of the length and sharpness of the permitted 
dagger will only help the strongest and most turbulent 
and leave die weaker at their mercy. You will all 
understand the meaning of this parable. It is true that 
we have a League of Nations and a Court of Arbitration. 
But the League is not much more than a meeting-hall 
and the Court has no means of enforcing its decisions. 
These institutions provide no security for any country 
in case of an attack on it. If you bear this in mind, you 
will judge die attitude of the French, their refusal to 
disarm without security, less harshly than it is usually 
judged at present. 

Unless we can agree to limit the sovereignty of die . 
individual state by all binding ourselves to take joint 
action against any country which openly or secretly 
resists a judgment of the Court of Arbitration, we shall 
never get out of a state of universal anarchy and terror. 
No sleight of hand can reconcile the unlimited sover- 
eignty of the individual country with security against 

attack. Will it need new disasters to induce the countries 

to undertake to enforce every decision of die recognised , 
international court? The progress of events so &r 
scarcely justifies us in hoping for anything better in die 
near future. But everyone who cares for civilisation 
and justice must exert all his strength to convince his ' 
fellow's of the necessity fcfr laying ah countries under 
an international obligation of this kind. 

It will be urged against this notion, not without a 
certain justification, that it over-estimates die efficacy of 
machinery, and neglects the psychological, or rather 
the moral, factor. Spiritual disarmament, people insist, 
must precede material disarmament. They say further, 

6a * 


and truly, that the greatest obstacle to international 
order is that monstrously exaggerated spirit of national- 
ism which also goes by the fair-sounding but misused 
name of patriotism During the last century and a half 
this idol has acquired an uncanny and exceedingly 
pernicious power everywhere 

To estimate this objection at its proper worth, one 
must realise, that a reciprocal relation exists between 
external machinery and internal states of mind Not 
only does the machinery depend on traditional modes 
of feeling and owe its origin and its survival to them, 
but the existing machinery in its turn exerases a power- 
ful influence on national modes of feeling 
The present deplorably high development of national- 
ism everywhere is, m my opinion, intimately connected 
with the institution of compulsory military service or, 
to call it by its less offensive name, national armies 
A country which demands military service of its 
inhabitants is compelled to cultivate a nationalistic spirit 
in them, which provides the psychological foundanon 
of military effiaency Along with this religion it has 
to hold up its instrument, brute force, to the admiration 
of the y outh m its schools 

The introduction of compulsory service is therefore, to 
my mind, the prune cause ofrhe moral collapse of the 
white race, which seriously threatens not merely the 
survival of our avilisauon but our very existence This 
curse, along with great soaal blessings, started with the 
French Revolution, and before long dragged all the 
other nations in its tram 

Therefore, those who desire to encourage the growth 
of an international spirit and to combat chauvinism 
must take their stand against compulsory' service Is the 
se\crc persecution to which consaenoous objectors to 


mill tar) service are subjected to-day a whit less dis- 
graceful to the community than those to which the 
mart)rs of religion were exposed m former centuries j 
Can ) ou, as the Kellogg Pact does, condemn war and 
at the same time leave the individual to the tender 
mercies of die wat maclune in each country » 

If, in view of the Disarmament Conference, we arc 
not to restrict ourselves to the technical problems of 
organisation involved but also to tackle die psjeho- 
logical question more dirccdy from educational 
motives, we must try on international lines to invent 
some legal way by which the individual can refuse to 
serve m the ami) Such a regulation would undoubtedly 
produce a great moral effect 

This is my position in a nutshell — Mere agreements 
to limit armaments furnish no sort of security Com- 
pulsory arbitration muse be supported by an executive 
force, guaranteed by all die participating countries, 
which is ready to proceed agamst the disturber of the 
peace with economic and military sanctions Compul- 
sory service, as the bulwark of unhealthy nationalism, 
must be combated, most important of all, conscientious 
objectors must be protected on an international basis 
Finally, I would draw your attention to a book, 
War again to-morrou , by Ludwig Bauer, which discusses 
the issues here involved in an acute and unprejudiced 
manner and with great psychological insight 


The benefits that the inventive genius of man has 
conferred on us in the last hundred years could make 
life happ) and care-free, if 'organisation had been able _ 
to keep pace with technical progress As it is, these 


hard-won achievements in the hands of our generation 
are like a razor in the hands of a child of three The 
possession of marvellous means of production has 
brought care and hunger instead of freedom 

The results of technical progress are most baleful 
where they furnish means for the destruction of human 
life and the hard-won fruits of toil, as we of the older 
generation experienced to our horror in the Great War 
More dreadful e\cn than the destruction, in my 
opinion, is the humiliating slavery mto which war 
plunges the individual Is it not a temble thing to be 
forced by the community to do things which every 
individual regards as abominable crimes? Only a few 
had die moral greatness to resist, them I regard as the 
real heroes of the Great War 
There is one ray of hope I believe that the respon- 
sible leaders of the nations do, in the main, honestly 
desire to abolish war The resistance to this essential 

step forward comes from those unfortunate national 
traditions which are handed on like a hereditary disease 
from generation to generation through the workings of 
die educational system The principal vehicle of tins 
tradition is military training and its glorification, and, 
equally, that portion of the Press which is controlled 
by heavy industry and the soldiers Without disarma- 
ment dierc can be no lasting peace Cons ersely , the 
continuation of military preparations on the present 
scale will mc\ itably lead to new catastrophes * 

That is wh\ the Disarmament Conference of 1932 
TOll decide die fate of dm generation and the next 
. " hen , onc dunks how pitiable, taken as a whole, hare 
been the results of fonuet conferences, ,t becomes clear 

- m 1 cxnt^h«r'f 3 m ' tUlEcnt md sponsible people 
to exert their full powers to remind pubhc opinion 



America and the Disarmament Conference 

The Americans of to-day are filled with the cares 
arising out of economic conditions in their own 
country. The efforts of their responsible leaders are 
directed primarily to remedying the serious unemploy- 
ment at home. The sense of being involved in the 
destiny of the rest of the world, and in particular of the 
mother country of Europe, is even less strong than in 
normal rimes. 

But the free play of economic forces will not by itself 
automatically overcome these difficulties. Regulative 
measures by the community are needed to bring about 
a sound distribution of labour and consumption- 
goods among mankind ; without them even the people 
of the richest country suffocate. The fact is that since 
the amount of work needed to supply everybody’s needs 
has been reduced through die improvement of tech- 
nical methods, the free play of economic forces no 
longer produces a state of affairs in which all the available 
labour can -find employment. Deliberate regulation 
and organisation arc becoming necessary to make the 
results of technical progress beneficial to all. 

If the economic situation cannot be cleared up without 
systematic regulation, how much more necessary is 
such regulation for dealing with the problems of 
international politics'. Few people still cling to the 
notion that acts of violence in the shape of wars are 
cither advantageous or worthy ofhumamty as a method 
of solving international problems. But they are not 
logical enough to make vigorous efforts on behalf of 
the measures winch might prevent war, that savage and 
unworthy relic of the age of barbarism. It requires 
some power of reflection to see the issue clearly and a 



certain courage to serve this great cause resolutely and 

Anybody who really wants to abolish war must 
resolutely declare himself in favour of his own country s 
resigning a portion of its sovereignty m favour of lnter- 
national institutions he must be ready to make his own 
country amenable, m case of a dispute, to the award of 
an international court He must in the most uncom- 
promising fashion support disarmament all r6und, 
which is actually envisaged m the unfortunate Treaty 
of Versailles , unless military and aggressively patriotic 
education is abolished, we can hope for no progress 
No event of the last few )ears reflects such disgrace 
on die leading civilised countries of the world as the 
failure of all disarmament conferences so far , for this 
failure is due not only to the intrigues of ambinous and 
unscrupulous politicians but also to the indifference and 
slackness of the public m all countries Unless this is 
changed wc shall destroy all the really valuable achieve- 
ments of our predecessors . 

I believe that the American nation is only imperfectly 
aware of the responsibility which rests with it m this 
matter People in America no doubt think as follows 
“Let Europe go to the dogs, if it is destroyed by the 
quarrelsomeness and wickedness of its inhabitants The 
good seed of our Wilson has produced a mighty P 00 ? 
crop in the stony ground ofEurope We are strong and 
safe and in no hurry to mix ourselves up in other 
people’s affairs ” , 

Such an attitude is at once base and short-sighted 
America is partly to blame for the difficulties ofEurope 
By ruthlessly pressing her claims she is hastening the 
economic and therewith the moral collapse ofEurope, 
she has helped to Balkamse Europe and therefore shares 

politics AND PACIFISM. 

the responsibility for the breakdown of political 
.morality and the growth of that spirit of revenge which 
feeds on despair. This spirit will not stop short of the 
gates of America— I had almost said, has not stopped 
short. Look around, and look forward. 

The truth can be briefly stated : — The Disarmament 
Conference comes as a final chance, to you no less than 
to us, of preserving the best that civilised humanity 
has produced. And it is on you, as the strongest and 
comparatively soundest among us, that the eyes and 
hopes of all are focussed. 

Active Pacifism 

1 consider myself lucky in witnessing the great peace 
demonstration organised by the Flemish people. To 
' all concerned in it l feel impelled to call out in the 
name of men of good will with a care for the future : 
“In tins hour of opened eyes and awakening conscience 
we feci ourselves united with you by the deepest ties.” 

We must not conceal from outselves that an improve- 
ment in the present depressing situation is impossible 
without a severe struggle; for die handful of diose 
who are really determined to do something is minute 
in comparison with the mass of the lukewarm and the 
* misguided. And those who have an interest in keeping 
the machinery of war going are a very powerful body; 
they will stop at nothing to make public opinion 
subservient to their murderous ends. 

It looks as if the ruling statesmen of to-day were 
really trying to secure permanent peace. But the 
ceaseless pihng-up of armaments shows only too clearly 
that they ate unequal to coping with the hostile forces 
which are prepanng for war. In my opinion, deliver- 

ance can only come from the peoples themselves If 
they 'wish, to avoid the degrading slaver) of vvar- 
service, they must declare with no uncertain voice for 
complete disarmament As long as armies exist, an) 
serious quarrel will lead to war A pacifism which docs 
not act uall y try to prev ent the nations from arming is 
and must remain impotent 

May the conscience and the common sense of the 
peoples be awakened, so that we may reach a new stag 6 
in the life of nations, where people will look back on 
war as an incomprehensible aberration of their fore- 
fathers 1 

Letter to a frtetu! of Peace 

It has come to m) ears that m >oui 
heartedness you arc quiedy accomplishing a 
work, impelled by solicitude for humanity 
fate Small is the number of them that see with their 
own e) es and feel with their own hearts But it is their 
strength that will decade whether the human race roust 
relapse into that hopeless condition which a him 
multitude appears to-day to regard as the ideal 

O that the nations nught sec, before it is too Jate, 
how much of their self-dctcrminauon they have got to 
sacrifice m order to avoid the struggle of all against an 
The power of conscience and die international s P inC 
has proved itself inadequate At present it is being so 
weak as to tolerate parley mg with the wont enenues 
of civilisation There is a bind of conaluuon which 
is a crime against humanity , and it passes for pound 

We cannot despair of humanity, since we arc our- 
selves human beings And it is a comfort that there still 

■ great- 
and its 


exist individuals like yourself, whom one knows to be 
alive and undismayed. 

• Another ditto 

Dear friend and spiritual brother. 

To be quite frank, a declaration like the one before 
me in a country which submits to conscription in peace- 
time-seems to me valueless. What you must fight for 
is liberation from universal military service. Verily the 
French nation has had to pay heavily for the victory 
of 1918; for that victory has been largely responsible 
for holding it down in the most degrading of all forms 
of slavery. Let your efforts in this struggle be unceasing. 
You have a mighty ally in the German reactionaries and 
militarists. If France clings to universal military service, 
it will be impossible in the. long run to prevent its* 
introduction into Germany. For the demand of the 
Germans ,for equal rights will succeed in the end ; and 
. , then there will be two German military slaves to every 
French one, which would certainly not be m the 
interests of France. 

Only if we succeed in abolishing compulsory service 
altogether will it be possible to educate the youth in 
the spirit of reconciliation, joy in life and love towards 
all living creatures. 

I believe that a refusal on conscientious grounds to 
serve in the army when called up, if carried out by 
50,000 men at the same moment, would be irresistible. 
The individual can accomplish little here, nor can one 
wish to see the best among us devoted to destruction 
through the machinery beliind tvhicli stand the three 
great powers of stupidity, fear, and greed. 


ance can only come from the peoples themselves If 
they wish to avoid the degrading slavery o war 
service, they must declare with no uncertain voice tor 
complete disarmament As long as armies exist, an) 
serious quarrel will lead to war A pacifism which does 
not actually try to prevent the nations from arming 
and must remain impotent - , 

May the conscience and the common sense 0 
peoples be awakened, so that we may reach a new g 
in the life of nations, where people will look ba 
war as an incomprehensible aberration of eir 

Letter to a friend of Peace 

It has come to my ears that m > our 
heartedness you are quietly accomplishing a S P , 
work, impelled by solicitude for humanity and lx 
fate Small is the number of them that so: wi 
own eyes and feci with their own hearts But it 
strength that will decide whether the human race 
relapse into that hopeless condinon which a 
multitude appears to-day to regard as die idea 
O that the nations ought see, before it is too • 
how much of their self-determination they have go 
sacrifice m order to avoid the struggle of all a S a “ lS 
The power of conscience and die intonation sp ^ 

has proved itself inadequate At present 
weak as to tolerate parleying with the worst enen •» 
of civilisation There is a land of conciliation w 
is a crime against humanity, and it passes for po ° 

We cannot despair of humanity, since we are our 
seh es human bangs And it is a comfort that there s 

it is being so 


exist individuals like yourself, whom one knows to be 
alive and undismayed. 

Another ditto 

Dear friend and spiritual brother, ‘ 

To be quite frank, a declaration like the one before 
me in a country which submits to conscription in peace- 
time seems to me valueless. What you must fight for 
is liberation from universal military service. Verily the 
French nation has had to pay heavily for the victory 
of 1918; for that victory has been largely responsible 
for holding it down in the most degrading of all forms 
of slavery. Let your efforts in this struggle be unceasing. 
You have a mighty ally in the German reactionaries and 
militarists. If France clings to universal military service, 
it will be impossible in the. long run to prevent its' 
introduction' into Germany. For the demand of the 
Germans ,for equal rights will succeed in the end ; and 
, then there will be two German military slaves to every 
French one, which would certainly not be in the 
interests of France. 

Only if we succeed in abolishing compulsory service 
altogether will it be possible to educate the youth in 
the spirit of reconciliation, joy in life and love towards 
all living creatures. 

I believe that a refusal on conscientious grounds to 
serve in the army when called up, if carried out by 
50,000 men at the same moment, would be irresistible. 
The individual can accomplish little here, nor can one 
wish to see the best among us devoted to destruction 
through the machinery behind which stand the three 
great powers of stupidity, fear, and greed. 



A third ditto 

Dear Sir, 

The point with which you deal in your letter is one 
of prime importance The armament industry is ** 
you sa) , one of die greatest dangers that beset manun 
It is the hidden evil power behind the nationalism whi t 
is rampant everywhere . 

Possibly something might be gained by nations * 
isanon But it is extremely hard to determine exact > 
what industries should be included Should the wen j 
industry* And how much ofihe metal industr) an 
the chemical industr) ? /■ 

As regards the munitions industry and the export o 
war material, the League of Nations has busied ttsf» 
for )ears with efforts to get this horrible traffic con- 
trolled— wnth what little success, we all Know La* 
)car I asked a w ell-known Amen can diplomat " Y 
Japan was not forced b> a commercial bojeott 
desist from her policy of force. “Our commerce 
interests arc too strong,” was the answer How cm 
one help people who rest sansfied wadi a jrarerv*n { 
like that t 


cate, but nothing can be*achieved as directly as you 

Women and War 

In my opinion, the patriotic women ought to be sent 
to the front in the next war instead of the men It 
would at least he a noyelty in this dreary sphere of 
infinite confusion, and besides — why should not such 
heroic feelings on the part of the fair sex find a more 
picturesque outlet than m attacks on a defenceless 

Thoughts on the World Economic Crisis 

If there is one thing that can give a layman m the 
sphere of economics the courage to express an opinion 
on the nature of the alarming economic difficulties of 
the present day, it is the hopeless confusion of opinions 
among the experts What I ha\e to say is nothing 
new and docs not pretend to be anything more 
than the opinion of an independent and honest 
man who, unburdened by class or national pre- 
judices, desires nothing but the good of humanity 
and the most harmonious possible scheme of human 
existence If m what follows I write as if I were clear 
about certain things and sure of the truth of what I 
am saying, tins is merely done for die sake of an easier 
mode of expression , it does not proceed from unwar- 
ranted self-confidence or a behetm the infallibility of 
piy somewhat simple intellectual conception of prob- 
lems which arc in reality uncommonly complex 

As 1 sec it, this crisis differs in character from past 
enses in that it is based on an entirely new set of con- 
ditions, due td rapid progress m methods of production 


A third ditto 

Dear Sir, 

The point with which you deal m your letter is one 
of prune importance The armament industry is & 
you sa) , one of the greatest dangers that beset manlon 
It is the hidden evil power behind the nationalism win 
is rampant everywhere . 

Possibly something might be gamed by nations i - 
isaaon But it is extremely hard to determine exact y 
what industries should be included Should uie aircra t 
industry ? And how much of the metal industry an 
die chemical industry ? r 

As regards the munitions industry and the export 
war material, the League of Nations has busied me 
for years with efforts to get this horrible traffic 
trolled — with what little success, we all know i-jn 
year I asked a well-known American diplomat w y 
Japan was not forced by a commercial bo>cott 
desist from her policy of force * Our eommer 
interests arc too strong,” was die answer How 
one help people who rest satisfied with a statemen 
like that ? - 

You believe that a word from me would sunicc 
gee something done in this sphere t What an illusion 
People flatter me as long as I do not get in their wa> 
But if I direct my efforts towards objects which do n 
suit them, they immediately rum to abuse and caiumn) 
in defence of their interests And the onlookers mos / 
keep out of the light, the cowards! Have you cji 
tested the avil courage of your countrymen* T c 
silendy accepted motto is”Leave it alone and dont 
speak of it” You may be sure that I shall do 
everything in my power along die lines you mdi- 


cate, but nothing can be ‘achieved as directly as you 

Women and War 

In my opinion, the patriotic women ought to be sent 
to the front in the next war instead of the men. It 
would at least be a novelty in this dreary sphere of 
infinite confusion, and besides — why should not such 
heroic feelings on the part of the fair sex find a more 
picturesque outlet than in attacks on a defenceless 
civilian * 

Thoughts on the World Economic Crisis 

If there is one thing that can give a layman in the 
sphere of economics the courage to express an opinion 
on the nature of the alarming economic difficulties of 
the present day, it is the hopeless confusion of opinions 
among the experts. What I have to say is nothing 
new and does not pretend to be anything more 
than the opinion of an independent and honest 
man who, unburdened by class or national pre- 
judices’, desires nothing but the good of humanity 
and the most harmonious possible scheme of human 
existence. If in what follows l write as if I were clear 
about certain things and sure of the truth of what I 
am saying, this is merely done for the sake of an easier 
mode of expression; it does not proceed from unwar- 
ranted self-confidence or a'belief in the infallibility of 
my somewhat ample intellectual conception of prob- 
lems which are in reality uncommonly complex 
te I see it, this crisis differs in character from past 
oases m that it is based on an entirely new set of con- 
ditions, due td rapid progress in methods of production 
’ 7i 


Only a fraction of the available human labour in the 
world is needed for the production of the total amount 
of consumption-goods necessary to life Under a 
completely free economic system this fact is bound to 
lead to unemployment For Reasons which I do not 
propose to analyse here, the majority of people are 
compelled to work for the minimum wage on which 
life can -be supported If two factories produce the same 
sort of goods, other things being equal, that one will 
be able to produce them more cheaply which employs 
less workmen — i e , makes the individual worker work 
as long and as hard as human nature permits From tins 
it follows inevitably that, with methods of production 
what they are to-day, only a portion of the available 
labour can be used While unreasonable demands arc 
made on this portion, the remainder is automatically 
excluded from the process of production This leads 
to a fall m sales and profits Businesses go smash, which 
further increases unemployment and diminishes con- 
fidence in industrial concerns and therewith public 
participation m these mediating banks, finally the 
banks become insolvent through the sudden with- 
drawal of deposits and the wheels of industry therewith 
come to a complete standstill 

The crisis has also been attributed to other causes 
which we will now consider 

(i) Oi ct-prodnetum We have to distinguish between 
two things here — real over-produenon and apparent 
ovcr-producuon By real over-produenon I mean a 
production so great that it exceeds die demand Tfus 
nny perhaps apply to motor-cars and wheat in the 
United States at the present moment, aldiough even 
that is doubtful By “over-produenon" people usually 
7 - 


mean a condition of things m which more of one 
particular article is produced than can, in existing 
circumstances, be sold, in spite of a shortage of con- 
sumption-goods among consumers This condition of 
things 1 call apparent over-production In this case 
it is not the demand that is lacking but the consumers’ 
purchasing-power Such apparent over-production is 
only another word for a crisis and therefore" cannot 
serve .as an explananon of the latter, hence people who 
try to make over-production responsible for die crisis 
are merely juggling with words 

(2) Reparations The obligation to pay reparations 
bes heavy on the debtor nauons and their industries, 
compels them to go in for dumpmg and so harms the 
creditor nations too This is beyond dispute But the 
appearance of the crisis in the United States, in spite 
of the high tanff-wall protecting them, proves that this 
cannot be the principal cause of die world crisis The 
shortage of gold in the debtor countries due to repara- 
tions can at most serve as an argument for putting an 
end to these payjpents, it cannot be dragged in as an 
explanauon/Stthc world cnsii 

' (3) Ermion of new tariff-walls Increase: tn the unpro- 
ductive burden of armaments Political insecurity owing to 
latent danger of ti ar All these things add considerably 
to the troubles of Europe but do not_matenally affect 
America The appearance of the crisis in America 
show’s that they cannot be its principal causes 

T he iroppiug-out of the two pouers, China and 
Russia Tins blow to world trade also does not touch 
America very .nearl) and dierefore cannot be a principal 
cause of die crisis 



(5) The economic rise of the lower classes since the War 
This, supposing it to be a reality, could only produce a 
scarcity of goods, not an excessive supply 

I will not weary the reader by enumerating further 
contentions which do not seem to me to get to the heart 
of the matter Of one thing I feel certain this same 
tcdmi cal progress which, m itself, might relieve mankind 
of a great part of the labour necessary to its subsistence, 
is the mam cause of our present troubles Hence there 
are those who would m all seriousness forbid the intro- 
duction of technical improvements This is obviousl) 
absurd But how can we find a more rational way out 
of our dilemma ? 

If we could somehow manage to prevent the pur- 
chasing-power of the masses, measured m terms of 
goods, from sinking below a certain minimum, stop- 
pages in the industrial cycle such as we arc experiencing 
to-day would be rendered impossible 

The logically simplest but also most daring method 
of achieving this is a completely planned econom), m 
which consumption-goods are produced and distributed 
by the community That, in essentials, is what is being 
attempted in Russia to-day Much will depend on 
what results this mighty experiment produces To 
hazard a prophecy here would be presumption Can 
goods be produced as economical!) under such a 
system as under one which leases more freedom to 
individual enterprise? Can this system maintain itself 
at all without the terror that has so far accompanied 
it, which none of us “westerners” would care to let 
himself in for? Does not such a rigid, centralised 
system 'fend towards protection and hostility to ad- 
vantageous innovations? We mjisr cake care, how- 
ever, not to allow these suspicions to become p re- 

judices which prevent us from forming an objective 
judgment. - 

My personal opinion is that those methods arc 
preferable which respect existing traditions and habits 
so far as that is in any way compatible with the end in 
view. Nor do I believe that a sudden transference of 
the control of industry to the hands of the public 
would be beneficial from the point of view of pro- 
duction ; private enterprise should be left its sphere of 
activity, in so far as it has not already been eliminated 
by industry itself in the form of cartelisation. 

There are, however, two respects in which this 
economic-freedom ought to be limited. In each branch 
of industry the number of working hours per week 
ought so to be reduced by law that unemployment is 
systematically abolished. At the same time minimum 
wages must be fixed in such a way that the purchasing 
power of the workers keeps pace with production. 

Further, in those industries which have become 
monopolistic in character through organisation on the 
part of the producers, prices must be controlled by the 
state in order to keep the creation of new capital within 
reasonable bounds and prevent the artificial strangling 
of production and consumption. 

In this way it nught perhaps be possible to establish 
a proper balance between production and consumption 
without too great a limitation of free enterprise and 
at the same time to stop the intolerable tyranny of the 
owners of the means of production (land, machinery) 
over the wage-earners, in the widest sense of the term 



Culture cud Prosperity 

If one would estimate the damage done b) the great 
political catastrophe to the development of human 
civilisation, one must remember that culture in its 
higher forms is a delicate plant which depends on a 
complicated set of conditions and is wont to flourish 
only m a few places at.any given time. For it to blossom 
there is needed, first of all, a certain degree of prosperity, 
which enables a fraction of the population to work at 
things not directly necessary to the maintenance of 
life , secondly, a moral tradition of respect for cultural 
values and achievements, m virtue of which this class 
is provided with the means of living by the other 
classes, those who provide the immediate necessities 
Of life f 

During the past century Germany has been one ot 
the countries m which both condinons were fulfilled 
The prosperity was, taken as a whole, modest but 
sufficient , the tradinon of respect for culture vigorous 
On this basis the German nanon has brought forth 
fruits of culture which form an integral part of the 
development of the modem w orld The tradinon, in 
the mam, sail stands, the prosperity is gone The 
industries of the country have been cut off almost 
completely from the sources of raw materials on 
which the existence of the industrial part of the 
populaoon was based The surplus necessary to support 
the intellectual worker has suddenly ceased to exirt 
With it the tradinon which depends on it will inevitably 
collapse also, and a fruitful nursery of culture turn to 
wilderness . 

The human race, m so far as u sets a value on culture, 
has an interest in preventing such impoverishment 


It will give what help it can in the immediate crisis 
and reawaken that higher community of feeling, now 
thrust into the background by national egotism, for 
which human values have a validity independent of 
politics and frontiers It will then procure for every 
nation conditions of work under which it can exist and 
under which it can bring forth fruits of culture. 

Production and Purchasing Power 

I do not believe that the remedy for our present 
difficulties lies in a knowledge of productive capacity 
and consumption, because this knowledge is likely, in 
the main, to come too late. Moreover the trouble m 
Germany seems to me to be not hypertrophy of the 
machinery of production but deficient purcliasmg power 
in a large section of the population, which has been 
cast out of the productive process through rational- 

The gold standard has, in my opinion, the serious 
disadvantage that a shortage in the supply of gold 
automatically leads to a contraction of credit and also 
of the amount of currency in circulation, to which 
contraction prices and wages cannot adjust themselves 
.sufficiently quickly.- The natural remedies for our 
troubles arc, m my opinion, as follows — 

(r) A. statutory reduction of working hours, gradu- 
ated for each department of industry, in order to get 
nd of unemployment, combined with the fixing of 
minimum wages for the purpose of adjusting die 
purchasing-power of the masses to the amount of goods 
available. & 

(2) Control of the amount of money m circulation 
and of the volume of credit in such a way as to keep 

the price-level steady, all special protection bem^ 
abolished , 

(3) Statutory limitation of pnccs for such articles 
as have been practically withdrawn from free com- 
petition by monopolies or the formation of cartels 

Production and Work 
An answer to Cederstrom 

Dear Herr Cederstrom, 

Thank you for sending me your proposals, which 
mterest me very much Having mvself given so much 
thought to this subject I feel that it is right that I should 
give you my perfectly frank opinion on them 

The fundamental trouble seems to me to be the 
almost unlimited freedom of the labour market com- 
bined with extraordinary progress in the methods or 
production To satisfy the needs of the world to-day 
nothing like all the available labour is wanted The 
result is unemployment and excessive competition 
among the workers, both of which reduce purchasing 
power and put the whole economic system intolerably 
out of gear 

I know Libera! economists maintain that every 
economy in labour is counterbalanced by an increase 
in demand But, to begin with, I don’t beheve it, 
and even if it were true, the above-mentioned factors 
would alwajs operate to force the standard of Irving 
of a large portion of the human race down to an 
unnaturally low level 

I also share )our conviction that steps absolutely 
must be taken to make it possible and necessar) for the 
younger people to take pan in the productive process 


Further, that tire older people ought to be excluded 
from certain sorts of work (which I call unqualified 
work), receiving instead a certain income, as having 
by that time done enough work of a kind accepted by 
society as productive. 

I too am in favour of abolishing large cities, but not 
of settling people of a particular type, c.g., old people, 
in particular towns. Frankly, die idea strikes me as 
horrible. I am also of opinion that fluctuations in die 
value of money must be avoided, by substituting for * 
the gold standard a standard based on certain classes of 
goods selected according to the conditions of con- 
sumption— as Keynes, if I am not mistaken, long ago 
proposed. With the introduction of this system one 
* might consent to a certain amount of “inflation,” as 
compared with the present monetary situation, if one 
could believe that the state would really make a rational 
use of the windfall thus accruing to it. 

The weaknesses of your plan lie, so it seems to me, 
in the sphere of psychology, or rather, in your neglect 
.of it. It is no accident that capitalism has brought with 
it progress not merely in production but also in know- 
ledge. Egoism and competmon are, alas, stronger 
(forces than public spirit and sense of duty. In Russia, 
they say, it is impossible to get a decent piece of bread. 

. . . Perhaps I am over-pessimistic concerning state 
and other forms of communal enterprise, but I expect 
little good from them. Bureaucracy is the death of all 
sound work. I have seen and experienced too many 
dreadful warnings, even in comparatively model 

I am inclined to the view that the state can only be 
of real use to industry as a limiting and regulative force. 
It must see to it that competition among the workers 


is kept widiin healthy limits, that all children arc give; 
a chance to develop soundly, and that wages arc big] 
enough for the goods produced to be consumed. Bu 
it can exert a decisive influence through its regularivi 
function if— and there again you arc right — its measure 
are framed in an objective spirit by independent experts 
I would like to write to you at greater length, bul 
cannot find the time. 


It seems to be a universal fact that minorities— 
especially when the individuals composing them are 
distinguished by physical peculiarities — are treated by 
the majorities among whom they live as an inferior 
order of beings The tragedy of such a fate lies not 
merely in the unfair treatment to which these minoririei 
are automatically subjected in social and economic 
matters, but also in the fact that under the suggestive^ 
influence of the majority most of the victims themsclve 
succumb to the same prejudice and regard their brethrd 
as inferior beings. This second and greater part of th 
evil can be overcome by closer combination and b 
deliberate education of the minority', whose spirit ui 
liberation can thus be accomplished. 

The efforts of the American negroes in th 
direction arc deserving of all commendation am 

Observations on the Present Situation in Europe 
The distinguishing feature of the present politic 
situation of the world, and in particular of Turo'i 
seems to me to be this, that political development 

Part III 




A S long as I have any choice, I will only stay in a 
country where political liberty, toleration, and 
equality of all citizens before the law are the rule 
Political liberty implies liberty to express one’s political 
views orally and in writing, toleration, respect for 
any and every individual opinion 
These conditions do not obtain m Germany at the 
present time Those who have done most for the cause 
of intemanonal understanding, among them some of 
the leading artists, are being persecuted there 

Any social organism can become psychically dis- 
tempered just as any individual can, especially in times 
of difficulty Nations usually survive these distempers 
I hope that healthy conditions will soon supervene in 
German) and that in future her great men like Kant 
and Goethe will not merely be commemorated from 
time to time but that the principles which they incul- 
cated will also prevail in public life and in the general 

March, 1933 

Correspondence with the Prussian Academy of Sciences 

The following correspondence is here published tor the first 
time m its authentic and complete form The version published 
m German newspapers was for the most part incorrect, im- 
portant sentences being omitted 

&nstm d ' m> ’ S dcckraHon of AP" 1 Is '. 1933, 3gauist 



The Prussian Academy of Sciences heard with 
indignation from the newspapers of Albert Einstein’s 
participation in atrocity -mongenng m France and 
America It immediate!) demanded an explanation 
In the meantime Einstein li3S announced his withdrawal 
from the Academy, giving as his reason that he cannot 
continue to serve the Prussian state under its presenr 
government Bcuig a Swiss citizen lie also, it seems 
intends to resign the Prussian nanonahev which he. 
acquired in 1913 simply by becoming a full member 
of the Acadcrm 

The Prussian Acadcm) of Sciences is particularly 
distressed b) Einstein's activities as an agitator in 
foreign countries, ss ir and its members haie always 
felt thcmsclv es bound b> the closest ties to the Prussian 
state and, while abstaining stneth from all political 
partisanslup, have alw a) s stressed and remained faithful 
to the national idea It has therefore, no reason to 
regret Emstcm s withdrawal 

Prof Dr Ernst Hcymann 
Perpetual Secretary 

Le Coq near Ostende April 5 th 1933 
To the Prussian Academy of Sciences 
I have received information from a thoroughh 
reliable source that die Academy of Sciences his spoken 
in an official statement of Einstein s participation in 
atrocity -mongenng in America and France 
I hereby declare that I have ne\er taken any part in 
atroar) mongenng and I must add that I have seen 
nothing of an) such mongenng anywhere In general 
people have contented themselves with reproducing 
and commenting on the official statements and orders 


of responsible members of the German government, 
together With the programme for the annihilation of 
the German jews by economic methods 
The statements I have issued to the Press were con- 
cerned with my intention to resign my posinon m the 
Academy and renounce my Prussian citizenship , I gave 
as my reason for these steps that I did not wish to live 
m a country where the individual does not enjoy 
equality before the law and freedom to say and teach 
what he likes 

Further, I described the present state of affairs in 
Qcrmany as a state of psychic distemper m the masses 
and also made some remarks about its causes 

In a written document which I allowed the Inter- 
national League for combating Anti-Semitism to make 
use of for die purpose of enlisting support and which 
was not intended for the Press at all, I also called upon 
all sensible people, who are still faithful to the ideals 
of a avihsanon m peril, to do their utmost to prevent 
this mass-psychosis, which is exhibiting itself in such 
terrible symptoms m Germany to-day, from spreading 

It would have been an easy matter for the Academy 
to get hold of a correct version of my words before 
issuing die sort of statement about me that it has The 
German Press has reproduced a deliberately distorted 
version of my words, as indeed was only to be expected 
with the Press muzzled as it is to-day 
1 am ready to stand by every word I have published 
In return, I expect the Academy to communicate this 
statement of mine to its members and also to the 
German public before which I hare been slandered 

3 "pSSr 1 a haad m s,imicnn s 



The Academy's answer of April nth, 1933 

The Academy would like to point out that its state- 
ment of April 1st, 1933, was based not ftierely-on Ger- 
man but principally on foreign, particularly French and 
Belgian, newspaper reports which Herr Einstein has 
not contradicted ; in addition, it had before it his much- 
canvassed statement to the League for combating 
anti-Semitism, in which he deplores Germany’s relapse 
into the barbarism, of long-passed ages. Moreover, the 
Academy lias reason to know’ that Herr Einstein, who 
according to his own statement has taken no part in 
atrodty-mongeriug, has at least done nothing to 
counteract unjust suspicions and slanders, which, in the 
opinion of the Academy, it was his 'duty as one of its 
senior members to do. -instead of that Herr Einstein 
has made statements, and in foreign countries at that, 
such as, coming from, a man of world-wide reputation, 
were bound td be exploited and abused by the enemies 
not merely of the present German government but of 
the whole German people. 

For the Prussian Academy of Sciences, 

(Signed) H. von Bcker, w 
E. Hcymann, 

Perpetual Secretaries. 

Berlin, April 7 th, 1933 
The Prussian Academy of Sciences. 

Professor Albert Einstein, Leyden, 

c/o Prof Ehrenfest, Witte Rosenstr. 

Dear Sir, 

As the present Principal Secretary of the Prussian 
Academy I beg to acknowledge the receipt of your 


communication, dated March 28 th anouncing your 
resignation of your membership of the Academy. The 
Academy took cognizance of your resignation in its 
plenary session of March 3 0t ^> 2933* 

While the Academy profoundly regrets the turn ' 
events have taken, this regret is inspired by the thought 
that a man of the highest scientific authority, whom • 
many years of work among Germans and many years 
of membership of our society must have made familiar 
with the German character and German habits of 
thought, should have chosen this moment to associate 
himself with a body of people abroad who — pardy no 
doubt through ignorance of actual conditions and 
events — have done much damage to our German 
people by disseminating erroneous views and un- 
founded rumours. We had confidendy expected that 
one who had belonged to our Academy for so long 
would have ranged himself, irrespective of his own 
political sympathies, on the side of the defenders of 
• our nation against the flood of lies which has been let 
loose upon it. In these days of mud-slinging, some of 
it vile, some of it ridiculous, a good word for the 
' German people from you in particular might have 
produced a great effect, especially abroad. Instead of 
which your testimony has served as a handle to the 
enemies not merely of the present Government hut 
of the German people. This lias come as a bitter and 
grievous disappointment to us, wliich would no doubt 
have led inevitably to a parting of the ways even if we ■ 
had not received )our resignation. 

Yours faithfully, 

(signed) von Ficker. 



Le Coq-sur-Mer, Belgium, 
April 12 th, 1933 

To the Prussian Academy of Sciences, Berlin 

I have received jour communication of the 7th 
instant and deep!) deplore the mental attitude displa) ed 
m it 

As regards the fact, I can on!) reply as f6llows — 
What you say about my behaviour is, at bottom, 
merely another form of the statement ) ou have already 
published, in which you accuse me of having taken 
part in atrocity-mongenng against the German nation 
I ha\e already, in my last letter, characterised this 
accusation as slanderous 

You have also remarked that a “good word” on my 
pan for “the German people” would have produced a 
great effect abroad To this I must reply that such a 
testimony as you suggest would hate been equivalent 
to a repudiation of all those notions of justice and 
liberty for which I have all my life stood Such a 
testimony would not be, as you put it, a good word 
for the German nation , on the contrary, it would only 
have helped the cause of those who are seeking to 
undermine die ideas and principles which have won 
for the German nation a place of honour in the civilised 
world By giving such a testimony in the present 
circumstances I should have been contributing, even « 
only indirectly, to the barbansanon of manners and 
the destruction of all existing cultural values 

It was for this reason that I felt compelled to resign 
from the Academy, and your letter only shows me how 
right I was to do so 


Munich, April 8 th, 1933 

From the Bavarian Academy of Sciences 
to Professor Albert Einstein. 


In your letter to the Prussian Academy of Sciences 
you have given the present state of affairs in Germany 
as the reason, for your resignation. The Bavarian 
Academy of Sciences, which some years ago elected 
you a corresponding member, is aUo a German 
Academy, closely allied to the Prussian and other 
German Academies; hence your withdrawal from 
the Prussian Academy of Sciences is bound to affect 
your relations with our Academy. 

We must therefore ask you how you envisage your 
relations with our Academy after what has passed 
between yourself and the Prussian Academy. 

The President of the Bavarian Academy of Sciences. 

Le Coq-sur-Mcr, April list, 1933 
To die Bavarian Academy of Sciences, Munich. 

I have given it as the reason for my resignation from 
the Prussian Academy that in the present circumstances 
I have no wish either to be a German citizen or to 
remain in a position of quasi-dependence on the 
Prussian Ministry of Education. 

These reasons would not, in themselves, involve 
the severing of my relations with the Bavarian Academy. 
If I nevertheless desire my name to be removed from 
the list of members, it is for a different reason. 

The primary duty of in Academy is to encourage 
and pro tea the scientific life of a country. The learned 

societies of Germany have, however — to the best of 
knowledge — stood by and said nothing while a not 
inconsiderable proportion of German savants and 
students, and also of professional men of unn crsity 
education, have been deprived of all chance of getting 
employment or earning their livings in Germany I 
would rather not belong to any soaet) which behaves 
m such a manner, even if it docs so under externa! 

A Reply 

The following hues are Einsteins answer to an mutation to 
assoaate himself with a French manifesto against Ann-Seminim 
m Germany 

I have considered this most important proposal, 
which has a bearing on several dungs diat l have nearl) 
at heart, carefully from every angle As a result I have 
come to the conclusion that I cannot take a pcrsonii 
partin dm cxtrcmcl) important affair, for two reasons — 

In the first place I am, after all, soil a German citizen, 
and in the second I am a Jew As regards die first point 
I must add that I have worked ui German institutions 
and have always been treated vvidi full confidence in 
German) However dccpl) I nn\ regret^ the thing! 
that arc being done there, however srrongl) I am 
bound to condemn die terrible mistakes diat are being 
made with the approval of die government, it » 
impossible for me to take part personal!) in an enter- 
prise set on foot b) responsible members of a foreign 
government In order that )ou mav appreciate tu* 
full), suppose that a French anzen in a more or I«J 
analogous situation had got up a protest against die 
Frencn government’s action 11 conjunction warn 

GERMANY I 9 3 3 

prominent German statesmen Even if you fully 
admitted that the protest was amply warranted by the 
facts, you would still, I expect, regard the behaviour 
of your fellow-citizen as an act of treachery If Zola 
had felt it necessary to leave France at the time of the 
Dreyfus case, he would sail certainly not have associated 
himself with a protest by German official personages, 
however much he might have approved of their acuon 
He would have confined himself to — blushing for his 
countrymen. In the second place, a protest against 
injustice and violence is incomparably more valuable 
if it comes entirely from people who have been 
prompted to it purely by sentiments of humanity and 
a love of jusace This cannot be said of a man like me, 
a Jew who regards other Jews as his brothers For him, 
an injustice done to the Jews is the same as an mjusnee 
done to himself He must not be the judge in his own 
case, but wait for the judgment of imparaal outsiders 
These arc my reasons But I should like to add that 
I have always honoured and admired that highly 
developed sense of justice which is one of the noblest 
features of the French tradinon 


Part IV 


Jewish Ideals 

T HE pursuit of knowledge for its own sake, <** 
almost fanatical love of justice, and the desire for 
personal independence — these tac the features of the 
Jewish tradition which make me thank my stars that 
I belong to it 

Those who arc raging to-day against the ideals of 
reason and individual liberty and are trying to establish 
a spiritless state-slavery by brute force rightly see in us 
their irreconcilable foes History has given us a difficult 
row to hoc , but so long as wc remain devoted servants 
of truth, justice and liberty, wc shall continue not 
merely to survive as die oldest of living peoples, 
but by creative work to bring Jorth fruits which con- 
tribute to the ennoblement of the human race, as 

Is there a Jewish point of view 7 

In the philosophical sense there is, m m\ opinion, 
no specifically Jewish outlook Judaism seems to 
me to be concerned almost cxclusn cly with the moral 
atntude in life and to life I look upon it as the essence 
of an atntude to life which is incarnate in the Jewish 
people rather dun the essence of the laws la*d down 
m the Thora and interpreted in die Talmud To me, 
die Thora and the Talmud arc merely the most import- 
ant evidence for the manner m which the Jewish 
conception of life held sway in earlier times 


The essence of that concepao^iecins to me to he 
in an affirmative attitude -'^-phe life of all creation 
The life of the ind-ridual has meaning m so far 
as it aids in malang the life of ever) living thing nobler 
an 1 »c beautiful Life is sacred — that is to $a), if 
the supreme value, to which all other values are 
subordinate The hallowing of the supra-individual 
life brings m its train a reverence for ever) thing 
spiritual— -a particularly characteristic feature of the 
Jewish tradition 

Judaism is not a creed the Jewish God is simply a 
negation of supersnoon, an imaginary result of its 
elimination It is also an attempt to base the moral law 
on fear, a regrettable and discreditable attempt Yet it 
seems to me that the strong moral tradition of the 
Jewish nanon has to a large extent shaken itself free 
from tills fear It is dear also that “serving God ’ was 
equated with “serving the living " The best of the 
Jewish people, especially the Prophets and Jesus con- 
tended nrelcsslv for this 

Judaism is thus no transcendental religion, it is con- 
cerned with hfc as wc hv c it and can up to a point grasp 
it, and nothing else It seems to me, therefore, doubtful 
whether it can be called a religion in the accented sense 
of the w ord, particular!) as no “faith” but die sanen- 
fi canon of hfc in a supra-personal sense is demanded of 
the Jew 

But the Jewish tradition also contains something 
else, something which finds splendid expresnon in 
man) of the Psalms namely, a sort of intoxicated jo) 
and amazement at the beauty and grandeur of this 
world, of which man can just form a Cunt notion- 
It is the feeling from which true sci'mniie research 
draws its spiritual sustenance, but which also seems to 


find expression in the song of birds To tack this on 
to the idea of God seems mere childish absurdity 
Is what 1 have described a distinguishing mark of 
Judaism l Is it to be found anywhere else under another 
name i In its pure form, nowhere, not even in Judaism, 
where the pure doctrine is obscured by much worship 
of the letter Yet Judaism seems to me one of its purest 
and most vigorous manifestations This applies parti- 
cularly to the fundamental principle of the sanctification 
of life 

It is characteristic that the animals were expressly 
included m the command to keep hoi) the Sabbath 
day, so strong was the feeling that the ideal demands 
the solidarity of all living things The insistence on 
the solidarity of all human beings finds still stronger 
expression, and it is no mere chance that the demands 
of Socialism were for the most part first raised by Jews 
How strongly developed this sense of the sanctity of 
life is in the Jewish people is admirably illustrated by a 
little remark which Walter Rathenau once made to 
me in conversation “-When a Jew says that he’s going 
hunting to amuse himself, he lies ” The Jewish sense 
of the sanctity of life could not be more simply 

Jewtsh Youth 

An ilttsii tr to a Questionnaire 

It IS important dm the young should be induced to 
tike an interest in Jewish questions end difficulties, and 
you deserve gratitude for devoting yourself to this task 

desl°m P f P t r i Th “ “ momc ? t not merely for the 
desuny of die Jews, whose welfare depends on their 
sucking together and helping each other, hut, overbid 

above that, for the cultivation of the international 
spirit, which is in danger everywhere to-day from a 
narrow-minded nationalism Here, since the days of 
the Prophets, one of the fiurest fields of acnwty has 
lain open to our nation, scattered as it is over the earth 
and only united by a common tradition 

Addresses on Reconstruction in Palestine 

Ten years ago, when I first had the pleasure o 
addressing you on behalf of the Zionist cause, oSt 
all our hopes were soil fixed on the future To-day 
we can look back on these ten years with joy, tor in 
that time the muted energies of die Jewish people nav 
accomplished a splendid piece of successful constructive 
work in Palestine, which certainly exceeds anything 
that we dared to hope then 
We have also successfully stood the severe test t 
which the events of the last few yean have subject 
us Ceaseless work, supported by a noble purpose 
leading slowly but surely to success The latest pro- 
nouncements of the British government in icatc 
return to a juster judgment of our case, this we rccog 
nisc with gratitude , 

But we must never forget what this crisis has taug 
us — namely, that the establishment of satisfactory 
relations between the Jews and the Arabs is uo 
England’s affair but ours We — that is to say, 
Arabs and ourselves— have got to agree on the mam 
outlines of an advantageous partnership which sna 
satisfy the needs of both- nations A just solution of 
problem and one worthy of both nations is an end no 


less important and no less worthy of our efforts than 
the promotion of the work of construction itself. 
Remember that Switzerland represents a higher stage 
of political development than any national state, 
precisely because of die .greater political problems 
which had to be solved before a stable community 
could be built up out of groups of different nationality 
Much remains to be done, but one at least of Herzl s 
aims has already been realised’ its task in Palestine has 
given the Jewish people an astonishing degree of 
solidarity and the optimism without which no organism 
can lead a healthy life 

Anything we may do for the common purpose is 
done not merely for our brothers m Palestine but for 
the well-being and honour of the whole Jewish people 

Wc are assembled to-day for the purpose of calling 
to mind our age-old community, its destiny and its 
problems It is a community of moral tradition, which 
has always shown its strength and vitality in nmes of 
stress In all ages it has produced men who embodied 
the conscience of the 'western world, defenders of human 
dignity and justice 

So long as we ourselves care about this community 
it will continue to exist to the benefit of mankind, in 
spite of the fact that it possesses no self-contained 
organisation A decade or two ago a group of far- 
sighted men, among whom Herzl of immortal memory 
stood out abose die rest, came to the conclusion that 
wc needed a spiritual centre m order to preserve our 
swsc of solidantj m d^icult tunes Thus arose the 

dea of Zionism and the work of settlement in Palestine 


the successful realisation of which we have been per- 
mitted to witness, at least in us highly promising 

I have had the privilege of seeing, to my great joy 
and satisfaction, how much this achievement has 
contributed to the recovery of the Jewish people, which 
is exposed, as a minority among the nations, not 
merely to external dangers but also to internal ones of 
a ps> chological nature 

The crisis which the work of construction has had to 
face in the last few years has lam heavy upon us and is 
not yet completely surmounted But the most recent 
reports show that the world, and especially the British 
government, is disposed to recognise the great things 
which he behind our struggle for the Zionist ideal 
Let us at this moment remember with gratitude our 
leader Wcizmann, whose zeal and circumspection have 
helped the good cause to success 

The difficulties wc have been through have also 
brought some good m their train They have shown us 
once more how strong the bond is which unites the 
Jews of all countries in a common destiny The crisis 
has also purified our attitude to the question of Palestine, 
purged it of the dross of nationalism It has been dearl) 
proclaimed that wc are not seeking to create a political 
society, but that our aim is, in accordance with the old 
tradition of Jewry, a cultural one in the widest sense of 
the word That bemg so, it is for us to soh e the problem 
of living side by side with our brother the Arab in an 
open, generous and worth) manner Wc ha\c here an. 
opportmut) of showing what we have learnt in the 
thousands of years of our martyrdom If we choose the 
nghc path we shall succeed and give the rest of the 
world a fine example 



Whatever we do for Palestine we do it for the honour 
and well-being of the whole Jewish people. 


I am delighted to have the opportunity of addressing 
a few words to the youth of this country which is 
faithful to the common aims of Jewry. Do not be 
discouraged by the difficulties which confront us in 
Palestine. Such things serve to test the will to live of 
our community. 

Certain proceedings and pronouncements of the 
English administration have been justly criticised. We 
must not, however, leave it at that but learn by experi- 

We need to pay great attention to our relations with 
. the Arabs. By cultivating these carefully we shall be 
able in future to prevent things from becoming so 
dangerously strained that people can take advantage 
of them to provoke acts of hostility. This goal is 
perfeedy within our reach, because our work of con- 
struction has been, and must continue to be, carried 
out in such a manner as to serve the real interests of the 
Arab population also. 

In this way we shall be able to avoid getting ourselves 
quite so often into the position, disagreeable for Jews 
and Arabs alike, of having to call in the mandatory 
power as arbitrator. We shall thereby be following not 
merely the dictates of Providence but also our traditions, 
which alone give the Jewish community meaning and 
stability. For that community is not, and must never 
become, a political one; this is the only permanent 
source whence it can draw new strength and the Only 
ground on which its existence can be justified. 




For the last two thousand years the common property 
of the Jewish people has consisted entirely ©fits past. 
Scattered over the wide world, our nation possessed 
nothing in common except its carefully guarded 
tradition. Individual Jews no doubt produced great 
work, but it seemed as if the Jewish people as a whole 
had not the strength left for great collective achieve- 

Now all that is changed. History has set us a great 
and noble task in the shape of active co-operarion in 
the building up of Palestine. Eminent members of our 
race arc already at work with all their might on the 
realisation of this aim The opportunity is presented 
to us of setting up centres of civilisation which the 
. whole Jewish people can regard as its work. We nurse 
the hope of erecting in Palestine a home of our own 
national culture which shall help to awaken the near 
East to new economic and spiritual life 

The object which the leaders of Zionism have Uj 
view is not a political but a social and cultural 
one The community m Palestine must approach the 
social ideal of our forefathers as it is laid down in the 
Bible, and at the same time become.a seat of modem 
intellectual life, a spiritual centre for the Jew of the 
whole world In accordance with tins notion, the 
establishment of a Jewish university in Jerusalem con- 
stitutes one of the most important amis of the Zionist 

During the last few months I have been to America 
in order to help to raise the material basis for this 
university there. The success of this enterprise was qmte 
natural. Thanks to the untiring energy and splendid 


sclf-sacrificing spirit of the Jewish doctors in America 
we have succeeded in collecting enough .money for the 
creation of a medical faculty, and the preliminary work 
is being started at once. After this success 1 have no 
doubt that the material basis for the other faculties 
will soon be forthcoming. The medical faculty is first 
of all to be developed as a research institute and to 
concentrate on making the country healthy, a most . 
important item in the work of development. Teaching 
on a large scale will only become important later on. 
As a number of highly competent scientific workers 
have already signified their readiness to take up 
appointments at the university, the establishment of a 
medical faculty seems to be placed beyond all doubt. 

I may add that a special fund for the university, entirely 
dis.tinct from die general fund for the development of 
the country, has been opened. For the latter consider- 
able sums have been collected during these months in 
America, thanks to the indefatigable labours of Pro- 
fessor 'Weizmann and other Zionist leaders, chiefly 
through the self-sacrificing spirit of the middle classes. 
1 conclude with a warm appeal to the Jews in Germany 
to contribute all they can, in spite of the present eco- 
nomic difficulties, for the building up of the Jewish 
home in Palestine. This is not a matter of charity but 
an enterprise which concerns all Jews and die success 
of whidi promises to be a source of the hiuhest satis- 
taction to all. 

en*?m“ J T Mcsn ?? u n °' J“' = charitable or colot 
3“^?' 3 P r ° b, ' m °/ central importance for 
Jewish people. Palcsnne is not primarily a place 


refuge for the Jews of Eastern Europe but the embodi- 
ment of the re-a wakening corporate spirit of the whole 
Jewish nation Is it the right moment for tins corporate 
sense to be awakened and strengthened? This is a 
question to which I feel compelled, not merel) by m> 
spontaneous feelings but on rational grounds, to return 
an unqualified “yes ” 

Let us just cast our eyes over the history of the lews 
in Germany dunng the past hundred yean A century 
ago our forefathers, with few exceptions, lived in the 
ghetto They were poor, without political rights, 
separated from the Genalcs by a barrier of religious 
traditions, habits of life and legal restrictions, their 
intellectual development was restricted to their own 
literature, and they had remained almost unaffected by 
the mighty advance of the European intellect which 
dates from the Renaissance And yet these obscure, 
humble people had one great advantage over us 
of them belonged in every fibre of his being to a com- 
munity in which he was completely absorbed, in wm cn 
he felt himself a fully privileged member, and which 
demanded nothing of hun mat was contrary to ™s 
natural habits of thought Our forefathers in those days 
were pretty poor specimens intellectually and ph) sically, 
but socially speaking they enjoyed an enviable spin tun 
equilibrium , 

Then came emancipation, which suddenly opened 
up undreamed-of possibilities to the individual Some 
few rapidly made a position for themselves m die 
higher walks of business and soaal life They greedily 
lapped up the splendid triumphs which the art and 
science of the western world had achieved The) 
joined m the process with burning enthusiasm, them- 
selves making contributions of lasting value At the 


same time they imitated the external forms of Gentile 
life, departed more and more from their religious and 
social traditions, and adopted Gentile customs, manners 
and habits of thought U seemed as though they were 
completely losing their identity m the superior numbers 
and more highly organised culture of the nations 
among whom they h\ ed, so that in a few generations 
there would be no trace of them left A complete dis- 
appearance of Jewish nationality in Central and Western 
Europe seemed inevitable 

But events turned out otherwise Nationalities of 
different race seem to have an instinct which prevents 
them from fusing However much the Jews adapted 
themselves, in language, manners and to a great extent 
even m the forms of religion, to the European peoples 
among whom they lived, the feeling of strangeness 
between the Jews and their hosts never disappeared 
This spontaneous feeling is the ultimate cause of anti- 
Semitism, which is therefore not to be got nd of by 
well-meaning propaganda Nationalities want to pur- 
sue their own path, not to blend A satisfactory state of 
affairs can only be brought about by mutual toleration 
and respect 

The first step m that direction is that we Jews should 
once more become conscious of our existence as a 
■nationality and regain the self-respect that is necessary 
to a healthy existence We must leam once more to 
glory in our ancestors and our history and once again 
take upon ourselves, as a nation, cultural tasks of a sort 
calculated to strengthen our sense of the community, 
it u not enough for us to play a part as individuals in 
the cultural development of the human race, we must 
also tackle tasks which only nations as a whole can 
pertonn Only so can the Jews regam social health 


It is from this point of view that I would have joo 
look at the Zionist movement To-day history has 
assigned to us the task of taking an acme part in the 
economic and cultural reconstruction of our native 
land Enthusiasts, men of brilliant gifts, have cleared 
the Waj, and many excellent members of our race arc 
prepared to devote themselves heart and soul to the 
cause May every one of them fully realise the import- 
ance of this work and contribute, according to his 
powers, to its success' 

The Jewish Community 
A speech in London 
Ladies and Gendemen, 

It is no easy matter for me to overcome my natural 
inclination to a life of quiet contemplation Sue 1 
could not remain deaf to the appeal of the O R.T and 
O Z E societies 1 , for in responding to it I am respond- 
ing, as it were, to the appeal of our sorely oppressed 
Jewish nation 

The posinon of our scattered Jewish community « 
a moral barometer for the political world For what 
surer index of political morality and respect for justice 
can there be than the attitude of the nauonS towards a 
defenceless mmont), whose pecuhanr) lies m th eir 
preservation of an ancient cultural track non ? 

This barometer is low at the present moment, as we 
arc painfully aware from the way we arc crested Sut 
it is this very lowness that confirms me in the conviction 
that it is our duty to preserve and consolidate our 
commumry Embedded in the tradition of the Jewish 
* Jar sh ch*nt»ble association* 


people there is a love of justice and reason which must 
continue to work for the good of all nations now and 
in the future In modem times this tradition has pro- 
duced Spinoza and Karl Marx 
Those who would preserve the spirit must also look 
after the body to which it is attached The O Z E 
society literally looks after the bodies of our people 
In. Eastern Europe it is working day and night to help 
our people there, on whom the economic depression 
has fallen particularly heavily, to keep body and soul 
together , while the ORT society is trying to get nd 
of a severe social and economic handicap under which 
the Jews have laboured since the Middle Ages Because 
we Were then excluded from all directly productive 
occupanons, we were forced into the purely commercial 
ones The only way of really helping the Jew in 
eastern countries is to give him access to new fields of 
activity, for winch he is struggling all over the world 
This is the grave problem which the O R.T society 
is successfully tackling 

It is to you English fellow-Jews that we now appeal 
to help us in tins great enterprise which splendid men 
have set on foot The last few years, nay, the last few 
days have brought us a disappointment which must 
have touched you in particular nearly Do not gird 
at fate but rather look on these events as a reason 
for remaining true to the cause of the Jewish com- 
monwealth I am convinced that m doing that 
wc shall also indirectly be promoting those general 
human ends which we must always recognise as the 

Remember that difficulties and obstacles are a valu- 
able source of health and strength to any society We 
should not have survived for thousands of > ears as a 
* 109 

community if our bed had been of roses, of that I am 

quite sure , 

r Bur we have a still fairer consolation Our friends 
are not exactly numerous, but among them arc men 
of noble spirit and strong sense of justice, who have 
devoted their lives to uplifting human society an 
liberating the individual from degrading oppression 
We are happy and fortunate to have such men from 
the Gentile world among us to-night, their presence 
lends an added solemnity to this memorable evening 
It gives me great pleasure to see before me Bemar 
Shaw and H G Wells, to whose view of life I am 

particularly attracted , 

You, Mr Shaw, have succeeded m winning the 
affection and joyous admiration of the world w e 
pursuing a path that has led many others to a mart) r s 
crown You have not merely preached moral sermo 
to your fellows, >ou have actually mocked at thing 
which many of them held sacred You has c done w a 
only the bom artist can do From ) our magic box >o 
have produced innumerable little figures which, w 
resembling human beings, arc compact not of Acs an 
blood but of brains, wit and charm And ) et in a way 
they are more human than we are ourselves, and on 
almost forgets that they are creations not of nature u 
of Bernard Shaw You make these charming Muc 
figures dance in a miniature world in front ot w 1 
the Graces stand sentinel and permit no bitterness to 
enter He who has looked into tins little world 
our actual world in a new light, its puppets m Jtn ^ 
ate themselves into real people, making them sue! e ) 
look quite different By thus holding die mirror UP t 
us all you have had a hbcranng effect on us suer 
hardly any other of our contemporaries has done an 



hive relieved life of something of its earth-bound 
heaviness. For this we are all devoutly grateful to you, 
and also cos&te, which along with grievous plagues has 
also given us the physician and liberator of out souls. 

I personally am also grateful to you for die unforgettable 
words which you have addressed to my mythical name- 
sake who makes life so difficult for me, although he is 
really, for all his clumsy, formidable size, quite a harm- 
less fellow. 

To you all I say that the existence and destiny of our 
people depends less on external factors than on ourselves 
remaining faithful to the moral traditions which have 
enabled us to survive for thousands of years despite the 
heavy storms that have broken over our heads. In the 
service of life sacrifice becomes grace, 

Working Palestine 

' Among Zionist organisations “Working Palestine’* 
is the one whose work is of most direct benefit to the 
most valuable class of people living there, namely those 
who ate transforming deserts into flourishing settle- 
ments by the labour of their hands. These workers are 
a selection, made on a voluntary basis, from the whole 
Jewish nation, an elite composed of strong, confident 
and unselfish people. They are not ignorant labourers 
who sell the labour of their hands to the highest bidder, 
hut educated, intellectually vigorous, free men, from 
whose peaceful struggle with a neglected soil the whole 
Jewish nation are the gainers, directly and indirectly. 
By lightening their heavy lot as far as we can we shall 
be saving the most valuable sort of human life; for the 
tint settlers struggle on ground not yet made habitable 


is a difficult and dangerous business involving a heavy 
personal sacrifice. How true this is, only they can 
judge who have seen it with their own eyes. Anyone 
who helps to improve the equipment of these men u 
helping on the good work at a crucial point. 

It is, moreover, this working class alone that has it 
in its power to establish healthy relations w™ ® 
Arabs, which is the most important political task o 
Zionism. Administrations come and go; but jt u 
human relations that finally turn the scale in the 
of nations. Therefore to support “Working Palestine 
is at the same rime to promote a humane and wor y 
policy in Palestine and to oppose an effective resistance 
those undercurrents of narrow nationalism from " * 
the whole political world, and in a less degree the smau 
political world of Palestine affairs, is suffering. 

Jewish Recovery 

I gladly accede to your paper’s request that I *ho 
address an appeal to the Jew’s of Hungary on be 
Keren Hajcssod. . 

The greatest enemies of the narional consaoi 
and honour of the Jews arc fatty degeneratxon-Dy 
which I mean the unconscionahlencss which c 
from wealth and case — and a kind of inner depen e 
on the surrounding Gentile world which co 
from the loosening of the fabric of Jewish 
The best in man can only flourish when lie loses tunwa 
in a community. Hence die moral danger ot C J«. 
who has lost touch with his own people and UT€&* 
as a foreigner by die people of his adoption . On ) 
often a conrcmptible and joyless egoism lias 1X5 ' , 

from such ' rircumsrances. The weight of outwi 


oppression on the Jewish people is particularly heavy at 
the moment Hut this very bitterness has done us good 
A revival of Jewish national life, such as the last genera- 
tion could never have dreamed of, has begun Through 
the operation of a newly awakened sense of solidarity 
among the Jews, the scheme of colonising Palestine, 
launched by a handful of devoted and judicious leaders 
m the face of apparently insuperable difficulties, has 
already prospered so far that I feel no doubt about its 
permanent success The value of this achievement for 
the Jews everywhere is very great Palestine will be a 
centre of culture for all Jews, a refuge for the most 
grievously oppressed, a field of action for die best 
among us, a unifying ideal, and a means of attaining 
inward health for the Jews of the whole world 

Antt-Semitism and Academic Youth 

So long as we lived in the ghetto our Jewish nation- 
ality involved for us material difficulties and sometimes 
physical danger, but no social or psychological prob- 
lems With emancipation the position changed, parti- 
cularly for those Jews who turned to the intellectual 
professions In school and at the university the young 
Jew is exposed to die influence of a society with a 
definite national tinge, which he respects and admires, 
from which he receives his mental sustenance, to which 
lie feels himself to belong, while it, on the other hand, 
treats him, as one of an alien race, with a certain con- 
tempt and hostility Driven by die suggestive influence 
ol this psychological superiority rather than by utili- 
tarian considerations, he turns his back on his people 
and his traditions, and considers himself as belongL 
cnnreU to the others while he mes m vam to conceal 


from himself and them the fact that-the' relation is not 
reciprocal. Hence that pathetic creature, die baptised 
Jewish Geheimrat of yesterday and to-day. In most 
cases it is not pushfulness and lack of character that ha\e 
made him what he is but, as I have said, the suggestive 
power of an environment superior in numbers an 
influence. He knows, of course, that many admirable 
sons of the Jewish people have made important contri- 
butions to the glory of European civilisation ; but base 
they not all, with a few exceptions, done much tfte 
same as he i . , . 

In this case, as in many mental disorders, die cure 
in a clear knowledge of one’s condition and its causes. 
We must be conscious of our alien race and draw 
logical conclusions from it. It is no use tr >™£ , 
convince die odiers of our spiritual and inte c 
equality by arguments addressed to the reason, w k 
their attitude does not originate in their intellects at • 
Rather must we emancipate ourselves socially and supp ) 
our social needs, in the mam, ourselves. We must n 
our own students’ societies and adopt an attitu 
courteous but consistent reserve to rhe Gennles 
let us live after our own fashion there and not . P 
duelling and drinking customs which are foreign ^ 
our nature It is possible to be a civilised 
and a good dozen and at the same time a faitmui J 
who loves lus race and honours his fathers. y ’ 

remember this and act accordingly, the problem 
anti-Semitism, in so far as it is of a social nature, 
solved for us 


A Letter to Professor Dr. Hellpach, Minister of State 
Dear Herr Hellpach, 

I have read your article on Zionism and the Zurich 
Congress and feel, as a strong devotee of the Zionist 
idea, that I must answer you, even if it is only shortly. 

The Jews are a community bound together by ties 
of blood and tradition, and not of religion only : the 
attitude of die rest of die world towards them is 
sufficient proof of this. When I came to Germany 
fifteen yean ago I discovered for the first time that I 
was a Jew, and I owe this discovery more to Gentiles 
than Jews. 

The tragedy of the Jews is that they are people of a 
definite historical type, who lack the support of a 
community to keep them together. The result is a 
want of solid foundations in the individual which 
amounts in its extremer forms to moral instability. 

I realised that die only possible salvation for die race 
was dm every Jew in the world should become attached 
to a living society to which the individual rejoiced to 
belong and which enabled him to bear the hatred and 
the 'humiliations that he has to put up with from the 
rest of the world. 

I saw worthy Jews basely caricatured, and the sight 
made my heart bleed. I saw how schools, comic papers 
and innumerable other forces of die Gentile majority 
undermined the confidence even of the best of my 
fcllow-Jews, and felt that tliis 'could not be allowed to 

. 1 realised that only a common enterprise dear 

to the hearts of Jews all over the world could restore 
this people to health. It was a great achievement of 



Herd's to have realised and proclaimed at the top of 
his voice that, the traditional attitude of the Jews being 
what it was, die establishment of a national home or, 
more accurately, a centre in Palestine, was a suitable 
obiect on which to concentrate our efforts. 

All this you call nationalism, and there is something 
in the accusation. But a communal purpose, wn thorn 
which we can neither live nor die in this hosnle w , 
can always be called by that ugly name, hi any « 
it is a nationalism whose aim is not power but dignity 
and health, lfwc did not have to live among mtotaan , 
narrow-minded and violent people, I sho | 

first to throw over all nationalism in favour o 

The obj ection that we Jews cannorbe P r0 P cr 
German state, for example, if we want «° 

of the 

f the German state, lor example, ; 

“ nanon,” is based on a misunderstanding “Tf 

of the state which springs from the nlto , jj 
national majorities. Against that Ultojeran . „ 

never be safe, whether we call ourselves a F°P‘ 

(or "nanon") or not. - e. ,, 1 -e 

I have put all this with brutal franlmess fo 
of brevity, but 1 know from your writings that ) 
a man who attends to the sense, not die lonn. 

Letter to an Arab 

March l Jlfc tP3° 

Your letter has given me great pleasure. 5“ 

that there is good will available on your side : to 
solnng the present difficulties in a manner w 
both our nations. I beheve that these diitic 
more psychological than real, and that thej can ^ 

* 116 


Zk if both sides bring honesty and good will to tb c 

1 >«K"A*L Prc T P0S ‘“ 0n » bad .s the fact 
before the mandatory°po\ver 'll 0dler “ ?PP? nents 
'“'Worth) of both nation. j ^ US S , tate op a ® urs IS 
0a { a „ “n Wkdfhod ^b/ altered ** 

< bffii l 'r B htbe y ° U h r!i 1 dllnJc th “ ^present 

dut this | only m^peison l‘ 42 ^ “ me 1 must 

ducus «d with nobody ? ! °P“*°n,- which I have 
because I am not dus ietKr m 

boghsh myself a,,j t not ca pable of writing it m 

tesponsibdity f 0 ?r You”LTf f '° bear tbe 
. f Pt, vy CoUnml .. .. , . 

A p" " conciliation to 

^AtabTsMi™^ 15 “ be for “'d to which' the jews 
to 0 ^ 1 PObn “>Tt“cT tanVeS ' Wh ° m “> 

Adoetot , , C ° mpOKd “Mows- 

A doctor 1 , ' ampoKd “folW_ 
Aw U T-S b b y y tf CdlalAs ~n : 

otlj nS men ’, , ™ la wyers , 

AnZl‘ ePre5 ' manve ’ ' ! «ted by the trade 

05 fa«uS l " mi. arc (o 

fores, o„ ” 0t t0 espouse *. , . 0I \ CC a wee k They 

° f 4t 't l “ n ° n but consaem™ 1 mtcrcsts ° f d'eir 
atm at the S y 3nd to dlc btst 
- • ° f *' country Th j m ' of th = whole 

Wd °! U,C country"' tu ' V ? lare of the whole 

fatum,! 4 ? ate StaCTln^!^" 30011 * sh aU be 

^ bu W°“' ,hera . esen°m dden “ 8 ‘ y= “>' 
teacher! „ m P n vate When a 
n an y subject lh winch not 


less than three members on each side concur, it may be 
published, but only m the name of the whole CouncU 
If a member dissents he may retire from the Coimai, 
but he is not thereby released from the obbganon o 
secrecy If one of the eleenve bodies above specified 
is dissatisfied with a resolunon of the Council, it may 
replace its representative by another 
Even if t l is “Pnvy Council has no definite powen 
it may ne, rtheless bring about the gradual composition 
of differences, and secure a united representanon of the 
common interests of the country before the mandatory 
power, clear of the dust of ephemeral polmcs 

Christianity and Judaism 

If one purges the Judaism of the 
Christianity as Jesus Christ taught it of all 
additions, especially diose of the priests, one is 1 
a teaching which is capable of cunng all die 

It is the^duty of every man of good wdl to 
stead fasti) m his own little world to make _ 

of pure humanity a living force so far as e 
males an honest attempt m this direction 
crushed and trampled under foot by his contempora 
hc’may consider himself and the community to 
he belongs lucky 

A Foreuord 

The following pages are devoted to an 3 PP^^ n ? c 
of the achievements of the German Jews t ^ 
remembered that we are concerned here with a > . 
people amounting in numbers, to no more 


population of a moderate-sized town, who have held 
their own against a hundred times as many Germans, 
in spite of handicaps and prejudices, through the 
superiority of their ancient cultural traditions Whatever 
attitude people may take up towards this little people, 
nobody who retains a shred of sound judgment in these 
times of confusion can deny them respect In these days 
of the persecution of the German Jews especially, it is 
time to remind the western world char it owes to the 
Jewish people (<i) its religion and therewith its most 
valuable moral ideals, and (6), to a large extent, the 
resurrection of the world of Greek though r Nor should 
it be forgotten that it was a translation of the Bible, that 
is to say, a translation from Hebrew, which broughr 
about die refinement and perfection of die German 
language To-day the Jews of Germany find their fairest 
consolation ui the thought of all they have produced 
and achieved for humanity by dieir efforts in modem 
tunes also, and no oppression however brutal, no 
campaign of calumny however subtle will blind those 
who have eyes to see to the intellectual and moral 
qualities inherent in this people 


Part V 


:hc use of mathematical language can. give. As regards 
us subject-matter, on the other hand, the physicist has 
:o limit himself very severely . he must content himself 
with describing die most simple events which can be 
brought, wi thin the domain of our experience ; all * 
svents of a more complex order are beyond the power* 
of the human intellect to reconstruct with the subdel 
accur acy a nd logi cal pe rfection which the dieoreHcal f 
physicist demands Supreme purity, clarity and cer- 
tainty are attained only by the sacrifice of completeness 
But what can be the attraction of getting to know such 
a tiny section of nature dioroughly, while one leaves 
everything subder and more complex shyly and 
timidly alonei Docs the product of such a modest 
effort deserve to be called by die proud name of a 
dicory of the Universe i 

In my belief the name is justified , for die general 
laws on which the structure of theoretical physics is 
based claim to be vahd for any natural phenomenon 
whatsoever. With them, it ought to be possible to 
amve at the description, that is to say, the theory, of 
f every natural process, mcludmg life, by means of pure 
deduction, if diat process of deduction were not 
far beyond die capacity of the human intellect 
The physicist’s renunciation of completeness for his 
cosmos is therefore not a matter of fundamental 

The supreme task of the physicist is to arrive at 
those universal elementary laws from which die cosmos 
can he built up by pure deduction There is no logical 
path to dicse laws, onl) intuition, resting on sympa- 
thetic understanding of experience, can reach them. , , 
In dm methodological uncertainty, one might suppose 
that there were any number of possible systems of 


theoretical ph)sics all with an equal amount to be said 
for diem , and this opinion is no doubt correct, theoret- 
ically But evolution has shown that at any given 
moment out of all conceivable constructions one has 
always proved itself absolutely superior to all the rest 
Nobody who has really gone deeply into the matter 
will deny that in practice the world of phenomena 
unambiguously determines the theoretical system, in spite 
of die fact that there is no logical bridge between 
phenomena and their theoretical principles, this is w at 
Leibnitz described so happily as a pre-cstabli 
harmony” Physicists often accuse epistemologists o 
not paying sufficient attention to this fact 1 

seems to me, he- the roots of die controversy carrie on 
some years ago between Mach and Planck , > 

The longmg to behold this pre-established harmo y 
is the source of the inexhaustible patience and endurance 
with which Planck lias devoted himself, as we see, to 
the most general problems of our science, refusing to 
let himself be dn erted to more grateful and more cas y 
attained ends I have often heard colleagues try to 
attribute this attitude of his to extraordinary wilI-pov.e 
and discipline — wrongly, m my opmion The 
mind which enables a man to do work of this ^ 
akin to that of the religious worshipper or the lo\er , 
daily effort comes from no deliberate intention or P ro “ 
gramme, but straight from the heart There he sim 
our beloved Planck, and smiles inside himself at my 
childish poking-about with the lantern of Diogenes 
Our affection for him needs no threadbare explanation. 
May the love of science continue to illumine his pa 
in the future and lead him to the solution of the mo 
important problem m present-day physics, wrn 
lias himself posed and done so much to sone MaN 


succeed in uniting die quantum-theory and electro- 
dynamics m a single logical system* ^ 

Inaugural Address to the Prussian Academy of Sciences < 



First of all, I have to thank you most heartily for 
conferring the greatest benefit on me that anybody can 
confer on such an one as myself By electing me to 
your Academy you have freed me from the distractions 
and cares of a professional life and so made it possible 
for me to devote myself entirely to saenufic studies 
I beg that you will connnue to believe in my grantude 
and my industry even when my efforts seem to )Ou to 
yield blit a poor result 

Perhaps 1 may be allowed & propos of this to make 
a few general remarks on the relation of my sphere of 
aenvit), which is theoretical physics, to experimental 
physics A mathematician friend of mind said to me 
the other day half in jest “The mathematician can do 
a lot of dungs, but never what ) ou happen to want just 
at the moment ” Much the same often applies to the 
theorencal physicist when the experimental physicist 
calls hun in What is the reason for this peculiar lack 
of adaptability 1 

The theorist’s method involves his using as his foun- 
dation general postulates or ‘principles” from which 
he can deduce conclusions His work thus falls into 
n\o parts He must first discover his principles and 
• men draw the conclusions which follow from them 
For the second of these tasks he receives an admirable 
equipment at school Once, therefore, he has per- 
formed the first in some department or for some com- 


plcx of related phenomena, he is certain of success, 
provided his industry and intelligence are adequate 
The first of these tasks, namely, that of establishing die 
principles which are to serve as die starting-point of 
his deduction, is of an entirely different nature Here 
there is no method capable of being learnt and system- 
atically applied that leads to the goal The scientist has' 
to worm dicse general principles out of nature by 
perceiving certain general features, which pemut of 
precise formulation, m large complexes of empirical 

Once tins formulation is successfully accomplished, 
mference follows on inference, often revealing relations 
which extend far bejond the province of reality from 
which the principles were originally drawn But as long 
as die principles capable of serving as starting-points for 
the deduction remain undiscovered, die individual fact 
is of no use to the theorist, indeed he cannot even do 
anything with isolated empirical generalisations of 
more or less wide application No, he has to persist in 
his helpless attitude towards die separate results of 
empirical research, until principles which he can make 
the basis of deductive reasoning have revealed them- 
selves to him 

This is the kind of position m which theory finds 
itself at present in regard to the laws of hcat-radiaaon 
and molecular movement-at low temperatures About 
fifteen years ago nobod) )Ct doubted that a correct 
account of the electrical, optical and thermal properties 
of bodies was possible on the basis of Gahleo-Newtoruan 
mechanics applied to the movement of molecules and 
of Clerk Maxwells dicory of the elcctro-magnenc 
field Then Planck showed that m order to establish 
a law of heat-radiation consonant with experience, it 
1 28 


was necessary to employ a method of calculation uhose 
mccmpoubUity wuli the principles of classical physics 
became clearer and dearer For with this method of 
calculation Planch introduced the quantum-hypothesis 
into physics, which has since received bnlhant con- 
firmation With this quantum-hypothesis he dethroned 
'classical physics as applied to the case where sunicscnuy 
small masses are mosed at sufficiently low speeds and 
high rates of acceleration, so that, to-day the law's of 
motion propounded by Galileo and Newton can only 
be allowed -validity as limiting law In spue of assi- 
duous efforts, however* the theorists have not yet 
succeeded in replacing the principles of mechanics by ' 
others which fit in with Planck’s law of heat-radiation 
or the quantum-hy pothesis No matter how definitely 
it has been proved that heat is to be explained by mole- 
cular movement, we have nevertheless to admit to-day 
that our position in regard to the fundamental laws of 
this motion resembles that of astronomers before 
Newton in regard to the mouons of the planets 
I have just now referred to a group of facts for the 
theorencal treatment of which the principles are lacking 
But it ma) equally well happen that clearly formulated * 
principles lead to conclusions which fall entirely, or 
almost entirely, outside the sphere of reality at present 
accessible to our experience In that case it may need 
many years of empirical research to ascertain whether 
die theoretical principles correspond with reality We 
have an instance of this in the theory of relativity 
n nnalvsis nf the .... _ /» ' 

velocity of bght “ . 0f ** ~ 

He %zr from 

- accept tbetheotyof,^™^ 


On the contrary, there is nothing to prevent our framing 
a general theory which takes account of the fact that 
in experiments earned out on the earth we are wholly 
unconscious of the earth's translator) motion This 
involves using the principle of relativity, which says 
that the laws of nature do not alter their form when 
one proceeds from the onginal (correctl) chosen) 
system of co-ordinates to a new one which is in uniform 
translatory motion with respect to it This theory has 
received impressive confirmation from experience and 
has led to a simplification of the theoretical description 
of groups of facts already connected together 

On the other hand, from the theoretical point of 
view this theory is not wholly satisfactory, because the 
principle of relativity just formulated prefers uniform 
motion If it is true that no absolute significance can 
be attached to uniform motion from the physical point 
of view, the question arises whether this statement must 
nor also be extended to non-umform motions It has 
become clear that one arrives at a quite definite enlarge- 
ment of the relativity theory if one postulates a principle 
of relativity in this extended sense One is led thereby 
to a general theory of gravitation which includes 
dynamics For the present, however, we have not the 
necessary array of frets to test the legitimacy of our 
introduction of the postulated principle 
We have ascertained that inductive physics asks 
questions of deductive, and vice versa to answer which 
demands the exertion of all our energies May wc soon 
succeed m making permanent progress by our united 
efforts 1 



Scientific Truth 

(l) It is difficult even to attach a precise meaning 
to the term “scientific truth. So different is the 
meaning of the word “truth” according as we arc 
dealing with a fact of experience, a mathematical pro- 
position or a scientific theory. Religious truth . 
conveys nothing clear to me at all, 

(2) Scientific research can reduce superstition by 
encouraging people to think and survey things in terms 
of cause and effect. Certain it is that a conviction, akin 
to religious feeding, of the rationality or intelligibility 
of the world lies behind all scientific work of a higher 

(3) The firm belief, which is bound up with deep 
feeling, in a superior mind revealing itself in the world 
of experience, represents my conception of God, which 
may therefore be described in common parlance as 
“pantheistic” (Spinoza). 

(4) Denominational traditions I can only consider 
historically and psychologically ; they have no other 
significance for me. 

The Method of Theoretical Physics 

If you want to find out anything from the theoretical 
physicists about the methods they use, I advise you to 
stick closely to one principle: don’t listen to their 
words, fix your attention on their deeds. To die dis- 
coverer in this field the products of his imagination 
appear so necessary and natural that he regards them 
and would have them regarded by others, not as 
creations of thought but as given realities. 

These words sound like an invitation to you to walk 


out of this lecture You will say to yourselves the 
fellow’s a working physi&st himself, and ought there- 
fore to leave all questions of die structure of theoretical 
sqence to the epistemologists 
Against such enaefsm I can defend m> self from the 
personal point of view by assuring you diat it is not at 
my own instance but at the hind invitation of others 
that I have mounted this rostrum, which serves to 
commemorate a man who fought hard all his life for 
the unity of knowledge Objectively, however, my 
enterprise can be justified on the ground dm it may, 
after all, be of interest to know how one looks upon his 
own branch of science who has spent a lifetime m 
striving with all lus nught to clear up and rectify its 
fundamentals The way m which he regards its past 
and present ma) depend too much on what he hppes 
for the future and aims at m the present, but that is 
the inevitable fate of anybody who has occupied himself 
intensively with a world of ideas The same thing 
happens to him as to the historian, who in the same wa), 
even diough perhaps unconsciously, groups actual events 
round ideals which he has formed for himself on the 
subject of human society 

Let us now cast an eye over the development of the 
theoretical system, paying special attenuon to die 
relations between die content of the theory and die 
totality- of empirical fact Wc arc concerned with the 
eternal antithesis between d e two inseparable com- 
ponents of our knowledge, the empirical and the 
rational, m our department 

We reverence ancient Greece as the cradle of western 
sacnce Here for the first time the world witnessed 
die miracle of a logical sjstem which proceeded from 
step to step with such precision that ever) .single one 


of its propositions was absolutely indubitable I refer 
to Euclid s geometry This admirable triumph of 
reasoning gave the human intellect the confidence in 
itself necessary for * its subsequent achievements If 
Euclid fails to kindle your youthful enthusiasm, then 
you were not bom to be a scientific thinker 
But before mankind could be npe for a science which 
takes in the whole of reality, a second fundamental 
truth was needed, which only became common pro- 
perty among philosophers with the advent of Kepler 
and Galileo Pure logical thinking cannot yield us any 
knowledge of the empirical world , all knowledge of 
reality starts froni cxpenence and ends in j t Proposi- 
u5ns”arnvccl-at byTpurcty logical means are completely 
empty as regards reality Because he saw this, and 
particularly because be drummed it into the scientific 
world, Galileo was the father of modem physics — 
indeed, of modem science altogether 
If, then, experience is the alpha and die omega of all 
our knowledge of reality, what is the function of pure 
reason m science ? 

A complete systejn of theoretical physics is made up 
of concepts, fundamental laws which are supposed to 
be valid for diosc concepts, and conclusions to be 
reached by logical deduction It is these conclusions 
which must correspond with our separate experiences , 
m an) theoretical treatise their logical deduction 
occupies almost the whole book 
This is exactly what happens in Euclid’s geometry, 
except that there the fundamental law arc called axioms 
and there is no question of the conclusions having to 
correspond to any sort of experience If, however, one 
regards Euclidean geometry' as die saencc of the mutual 
posiQonal^rclaaons of practically ngid bodies m space, 


that is to say, treats it as a physical science, without 
abstracting from its original empirical content, the 
logical homogeneity of geometry and theoretical 
physics becomes complete 
We have thus assigned to pure reason and experience 
their places m a theoretical system of physics The 
structure of the system is the work of reason, the 
empirical contents and their mutual relations must find 
their representation in the conclusions of the theory In 
the possibility of such a representation lies the sole value 
and justification of the whole system, and especially of 
the concepts and fundamental principles which under- 
lie it These latter, by the way, are free inventions of the 
human intellect, which cannot be justified cither by the 
nature of that intellect or in any other fashion a priori 
These fundamental concepts and postulates, which 
cannot be further reduced logically, form the essential 
pare of a theory, which reason cannot touch it « the ^ 
grand object of all theory to make these irreducible 
elements as simple and as few in number as possible, 
without having to renounce the adequate representation 
of any empirical content whatev cr 
The view I have just outlined of the purely fictitious 
character of die fundamentals of scientific theory was 
by no means the prevailing one m the eighteenth or even 
the nineteenth century But it is steadily earning ground 
from the fact that the distance in thought between the 
fundamental concepts and laws on one side and, on the 
other, the conclusions wluch have to be brought into 
relation with our experience grows larger and larger, 
the simpler the logical structure becomes — that is to 
say, the smaller die number of logically independent 
conceptual elements which are found necessary to 
support the structure # 



Newton, the first creator of a comprehensive, work- 
able system of theoretical physics, still believed that the 
basic concepts and laws of his system could be derived 
from experience. This is no doubt the meaning of his 
saying, hypotheses von jingo. 

Actually the concepts of time and space appeared at 
that time to present no difficulties. The concepts of 
mass, inertia and force, and the laws connecting them 
seemed to be drawn directly from experience. Once 
this basis is accepted, the expression for die force of 
gravitation appears derivable from experience, and it 
was reasonable to hope for the same in regard to other 

"Wc can indeed see from Newtons formulation of it 
that the concept of absolute space, which comprised 
that of absolute rest, made him feel uncomfortable; he 
realised that there seemed to be nothing in experience 
corresponding to this last concept. He was also not 
• quite comfortable about the introduction of forces 
operating at a distance. But the tremendous practical 
success of his doctrines may well have prevented him 
and the physicists o c the eighteenth and nineteenth 
centuries from recognising the fictitious character of 
the foundations of his system. 

The natural philosophers of those days were, on the 
contrary, most of them possessed with the idea that 
the fundamental concepts and postulates of physics 
were not in the logical sense free inventions of the 
human mind hut could be deduced from experience by 
abstraction —that is to say by logical means. A dear 
recognition of tht moneousness of tnis notion really 
only came with the general theory of relativity, which 
showed that one could take account of a wider range of 
empirical facts, and that too in a more satisfactory and 
- *35 


complete manner, on a foundation quite different from 
die Newtonian than was possible with it But quite 
apart from the quesaon which is superior, the ficnaous 
character of fundamental principles is perfectly evident 
from die fact diat wc can point to two essentially differ- 
ent principles, both of which correspond with experience 
to a large extent, this proves at the same time that every 
attempt at a logical deduction of the basic concepts and 
postulates of mechanics from elementary experiences is 
doomed to failure 

If, then, it is true that this axiomatic basis of theo- 
retical physics cannot be extracted from experience but 
must be freely invented, can we ever hope to ibid the 
right way ? Na> more, has this nght way any existence 
outside our illusions i Can we hope to be guided in the 
nght way by experience when there exist theories (such 
as classical mechanics) which to a large extent do justice 
to expenence, without getting to the root of the matter I 
I answer without hesitation that there is, in my opinion, 
a nght way, and that we are capable of finding it. Out 
expenence hitherto justifies us in behoving that nature 
is the realisanon of the simplest conceivable mathematical 
ideas I am convinced that we can discover b> means 
of purely mathematical constructions die concepts and 
the laws connecting them with each other, which furnish 
the key to the understanding of natural phenomena. 
Expenence may suggest the appropnate mathematical 
concepts, but they most certainly cannot be deduced 
from it Expenence remains, of course, the sole 
entenon of the physical utility of a mathemancal con- 
struction But the creative principle resides in mathe- 
matics In a certain sense, therefore, I hold it true that 
pure thought can grasp reality, as the ancients dreamed 
In order to justify this confidence, I ain compelled 


to make use of a mathematical conception. The 
physical world is represented as a four-dimensional 
continuum. If I assume a Ricmannian metric in it and 
ask what arc the simplest laws which such a metric can 
satisfy, I amve at the relativist theory of gravitation in 
empty space. If in that space I assume a vector-field or 
an anti-symmetrical tensor-field which can be inferred 
from it, and ask what are the simplest laws which such 
a field can satisfy, I arrive at Clerk Maxwell’s equations 
for empty space. 

At this point we still lack a theory for those parts of 
space in which electrical density does not disappear. 
De Broglie conjectured the existence of a wave-field, 
.which served to explain certain quantum properties of 
matter. Dirac found in the spinors field-magnitudes of 
a new sort, whose simplest equations enable one to a 
large extent to deduce the properties of the electron. 
Subsequently I discovered, in conjunction with my 
e3! dl ? c s P“ 10rs f° rm 3 special case of anew 
2” ° mathematically connected with the four- 
dimensional system, which we called “semivectors.” 

be re3?f eq -l d0n f l ° which such semivectors can 
e^ t e e d n ^n/ UnUSh " k 7, t0 die ““demanding of the 
eTnonde-U ° SOrtS particles, of dtffer- 

chsrcc Th C ^ e<Jual tut °PP osite electrical 
StoW T™*? 0 ? are, »f«r ordinary vectors. 

«mXr W Tr d fi ? Ids ™ P«Me in a 

if they desribed™ ° f four dlmm stons, and it looks as 

CSSL Sf “ * observe is that aU 
arrived at by die nri connecting them can be 



In the limited nature of the mathematically existent 
simple fields and the simple equations possible between 
them lies the theorist’s hope of grasping the real in all 
its depth 

Meanwhile the great stumbling-block for a field- 
theory of this land hes in the conception of the atomic 
structure of matter and energy For the theory is 
fundamentally non-atomic in so far as it operates 
exclusively with continuous functions of space, in 
contrast to classical mechanics, whose most important 
element, the material pomt, in itself -mounts for the 
atomic structure of matter 

The modem quantum theory in the form associated 
with the names of de Broglie, Schrodinger, and Dirac, 
which operates with continuous funenons, has over- 
come these difficulties by a bold piece of interpretation 
which was first given a dear form by Max Bom 
According to this, the spatial funenons which appear 
in the equanons make no daun to be a mathematical 
model of the atomic structure Those funenons are 
only supposed to determine the mathemancal proba- 
bihues of such structures occurring if measurements 
were taken at a particular spot or in a certain state of 
monon Tlus notion is logically unobjecnonable and 
has important successes to its credit Unfortunately, 
however, it compels one to use a continuum the 
number of whose dimensions is not that ascribed to 
space by physics hitherto (four) but rises indefinitely 
with the number of the parades consntuung the s)stem 
under considcranon I cannot but confess that I attach 
only a transitory importance to tins interpretation I 
soil beheve in die possibility of a model of reality— 
that is to sa) , of a theory which represents dungs them- 
sdves and not merely the probability of their occurrence 



On the other hand it seems to me certain that we 
must give up the idea of a complete localisation of the 
particles In a theoretical model. This seems to me to 
be the permanent upshot of Heisenberg s Uncertainty 
Principle. But an atomic theory in the true sense of 
the word (not merely on the basis of an interpretation), 
without localisation of particles in a mathematical 
model, is perfectly thinkable. For instance, to account 
for the atomic character of electricity, the field equations 
need only lead to the following conclusion : — A portion 
of space (three-dimensional) at whose boundaries 
electrical density everywhere disappears, always con- 
tains a total electrical charge whose size is represented 
by a whole number. In. a continuum-theory, atomic 
characteristics would be satisfactorily expressed by 
integral laws without localisation of the formation 
which constitutes the atomic structure. 

Not until the atomic structure had been successfully 
represented in such a manner would 1 consider the 
quantuin-nddle solved. 

Address at Columbia University, New York 

Science as something existing and complete is the * 
most objective thing known to man. But science in the 
making, science as an end to be pursued, is as subjective 
and psychologically conditioned as any other branch of 
human endeavour— so much so that the question, 
"What is the purpose and meaning of science? receives 
quue different answers at different rimes and. fewa. 
different sorts of people. 

\r’t^ COURC ’. univcrs % agreed that science has to 
establish connections between the facts of experience, 
ot such a kind that we can predict further occurrences 


from those alrcad) experienced Indeed, according to the 
opinion of man) positivists the completes! possible 
accomplishment of this task is die only end of science 
I do not believe, however, that so elementary an 
ideal could do much to kindle the m\ esagator's passion, 
from which really great achievements have arisen 
Behind the tireless efforts of the investigator there lurks 
a stronger, more mjstcnous drive it is existence and 
reality that one wishes to comprehend But one shrinks 
from the use of such words, for one soon gets into 
difficulties when one has to explain what is real/) meant 
b) “reality” and b) “comprehend” in such a general 

When w e strip the statement of its mystical elements 
vve mean that vve arc seeking for the simplest possible 
s) stem of thought winch will bind togedier the observed 
facts By die “simplest” s)$tcm we do not mean die 
one which die srudent wall have die least trouble m 
assimilating, but the one which contains the fewest 
possible mutually independent postulates or axioms, 
since the content of diesc logical, mutuall) independent 
axioms represents that remainder which is not com- 

When a man is talking about scientific subjects, the 
little word “I ’ should pla) no part in Jm exposition 
But when he is talking about die purposes ana aims of 
science, he should be pemutted to speak of himself, 
for a man experiences no aims and desires so immedi- 
atel) as his own The special aim which I have eon- 
stantl) kept before me is logical umficanon in die field 
of phj’sics To start with, it disturbed me that electro- 
dynamics should pick out ewe state of motion in prefer- 
ence toothers, without an> experimental’ juwmcrfltf® 
for dm preferential treatment Tints arose die special 


theory of relativity, -which, moreover, welded together 
into scomprchensible unities the electrical and magnetic 
fields, as well as mass and energy, or momentum and 
energy, as the case may be. Then out of the endeavour 
to understand inertia and gravitation as having a unified 
character there arose die general theory’ of relativity/ 
which also avoided those implicit axioms which underlie 
our thinking when we use special co-ordinate systems 
in the process of formulating^ basic laws. 

At the present time it is particularly disturbing that 
the gravitational field and the electrical field should 
enter into the theory' as mutually independent funda- 
mental concepts After many years of effort, however, 
an appropriate logical unification has been achieved— 
t I VC ~ thr0US l 1 a new H^themaucal method, 

coUaborat: ^ ******** 

^ Cre saU rcmams ““Standing an 
£ “ of * e kmd, which has often 

HEV b , ut found no sausfactory 

in terms of r “Puliation atomic structure 
based on 1, ® ekb " tbcor y All these endeavours are 
comple,"K ha^ nV1 ' COOn ' hat eldsten “ *Wld have a 
Etot^d !t “- T °- day we have k » 

forced awav fro ^ rc for . ^owmg ourselves to be 
from this wonderful behef. 

Johannes Kepler 

dttSSli— ““ when it h 
\nman *' oi 

*e serene greatness of y ^ t0 °< 

■ »n™ SiStfCi s 



an accepted certainty How great must ins faith in 
natural law have been, to have given him the strength 
to devote ten y ears of hard and patient work to the 
empirical investigation of the movement of the planers 
and the mathematical laws of that movement, entirely 
on his own account, supported by no one and under- 
stood by very few* If we would honour his memory 
worthily, we must get as clear a picture as we can of his 
problem and the stages of us solution t 
Copernicus had opened die eyes of the most intelligent 
to the fact that the best way to get a clear grasp of die 
apparent movements of the planets in the heavens was 
by regarding them as movements round the sun con- 
ceived as stationary If the planets mov ed uniform 1) m 
a circle round the sun, it would have been compara- 
tively easy to discover how these movements must 
look from the earth Since, however, the phenomena 
to be dealt with were much more complicated than 
that, the rask was a far harder one The first thing to 
be done was to determine these movements empirically 
from the observations of Tycho Brahe Onl) then did 
it become possible to think about discovering the 
general laws which these movements satisfy 

To grasp how difficult a business it wms cv en to luid 
out about die actual movements of revolution, one has to 
realise the following One can never see w here a planer 
real]) is a r any given moment, bur only in what direcuon 
it is seen just then from die eardi, which however, 
is itself moving in an unknown manner round the sun 
The difficulties dius seemed practically unsurmounfable 
Kepler had to discov cr a way of bringing order into 
this chaos To start with, he saw that it was ncccssarv 
first to try to find out about the monon of the earth 
itself This would have been simply impossible » 

J 42 


there had existed only the sun, the earth and thefed 
stars, but no other planets For in that case one coulov 
ascertain nothing empirically except how the direction 
of the straight line sun-earth changes in the course of 
the year (apparent movement of the sun with refer- 
ence to the fixed stars) In this way it was possible to 
discover that these directions all lav in a plane stationary 
with reference to the fixed stars, at least with the 
accuracy of observation achieved in those days, when 
there were no telescopes By this means it could also 
be ascertained m what manner the line sun-earth 
revolves round the sun It turned out that the angular 
velocity of this monon went through a regular change 
in die course of die y car But this was not of much use, 
as it was still not known how the distance between the 
earth and die sun alters in the course of the year It 
was only when these changes were known that die real 
shape of die earth's orbit and the manner in which it is 
described were discovered 

Kepler found a marvellous way out of dns dilemma 
In the first place, it followed from the observations of 
the sun that the apparent path of the sun against die 
background of die fixed stars differed m speed at 
different times of die year, but that the angular vclocitv 
of this movement was always die same at the same 
•point in die astronomical year, and dicrefore that die 
speed of rotation of the straight line cardi-sun was 
r' I? 5 ^ ,C sarnc "hen it pointed to die same region 
u i s , tars ^ was dius legitimate to suppose 
that die earth s orbit was a self-enclosed one, described 
o> die earth in the same way cvcrv year— which was 
> no means obvious a prion For die adherent of die 
Copcrnican sy stem it was dius as good as certain that this 
must also apply to die orbits of the rest of the planets 


This certainly nude things easier But how to ascer- 
c tain die real shape of the earth s orbit * Ima£ mc a bnghtly 
shining lantern M somewhere in the pknc of the 
orbit We know that this lantern remain 5 permanently 
in its place and thus forms a kind of fixed tnangulanon- 
point for determining the earth’s orbit, 4 point which 
the inhabitants of the earth can take a sitjht on at 311 >’ 
time of y ear Let this lantern M be farther awa > l* rom 
the sun than the earth With the help of suc h a hmrern 
it "was possible to determine die earth’s orbit, in the 
following way — 

First of all, in every year there come 5 a moment 
when the earth E lies exactly on the hnf joining the 
sun S and the lantern M If at this moir^t 1°°* 
from the earth B at the lantern M, our n* 16 0 * ‘ 5t S lA 
will comade with the line SM (sun-lantel* 1 ) Suppose 
the latter to be marked in the heavens fd° w imagine 
the earth m a different posinon and at a deferent time 
Since the sun S and the lantern M can b 0 ^ 1 ^ CJ1 
from the earth, the angle at E m die maPg‘ c SEM is 
known But we also know' die direction SE m 
relation to the fixed stars through direct w** observa- 
tions, while the direction of the line SM U* rclanon to 
the fixed stars was finally ascertained prc\' 10m |> 
in the triangle SEM vve also know the ^S* 6 at 
Tlicrcforc, with the base SM arbitrarily hfd dowjn on 
a sheer of paper, wc can, m virtue of out 
of the angles at E and S, construct the tn^gk 
We might do dus at frequent intervals during the year, 
cadi time we should get on our piece ofpap^ 3 posmon 
bf the eardi E with a date atrachcd to it arid a ceit^i 
posmon m relation to the permanently fixed baseS 
The earth's orbit would thereby be empin^ 1 ) 
mined, apart from its absolute sue, of co ufl* 



‘ But, you will say, where did Kepler get fir Untsrn 
M » His genius and Nature, benevolent in this 'Casr* 
gave it to him There was, for example, the planet 
Mars, and the length of the Martian year— i e , one 
rotanon of Mars round the 'Sun — was known It may 
happen one fine day that the sun, the earth and Mars 
he absolutely in the same straight line This position of 
Mars regularly recurs after one, two, etc Maroan 
years, as Mars has a self-enclosed orbit At these known 
moments, therefore, SM always presents the same 
base, while the earth is always at a different point in 
its orbit The observations of the sun and Mars at these 
moments thus constitute a means of determining the 
true orbit of the earth, as Mars then plays the part of 
our imaginary lantern Thus it was that Kepler dis- 
covered the true shape of the earth’s orbit and the 
way m which the earth describes it, and we who come 
after— Europeans, Germans, or even Swabians — may 
well admire and honour him for it 
Now that the earth’s orbit had been empirically 
determined, the true position and length of the line SE 
at anv moment was known, and it was not so terribly 
difficult for Kepler to calculate the orbit and motions 
of the rest of the planets too from observations — at least 
m principle It was nevertheless an immense work, es- 
pecially considering the state of mathematics at the time 
Nov, came the second and no less arduous part of 
Kepler’s hfc-vv ork The orbits were empirically known, 
but their laws had to be deduced from the empirical 
data. First he had to make a guess at the mathematical 
nature of the curve described by the orbit, and then 
«y it out on a \ ast assemblage of figures If it did not 
fit, another hypothesis had to be devised ard again 
tested After tremendous search, the conjecture that 


th£/ 6 rbit was an ellipse with the sun at one of its foci 
'was found to fir the facts Kepler also discovered the 
law governing die variation in speed during rotation, 
which is that the line sun-planet sweeps out equal areas 
in equal periods of nine Finally he also discovered 
that the square of the period of circulation round the 
sun vanes as the cube of the major axes of the ellipse 

Our admiration for this splendid man is accompanied 
by another feeling of admiranon and reverence, the 
object of which is no man but the mvstenous harmony 
of nature into which we are bom As far back as 
ancient times people devised the lines exhibiting the 
simplest conceivable form of regularity Among these, 
next to the straight line and the arcle, the most import- 
ant were the ellipse and the hyperbola We see the last 
two embodied — at least very nearly so — in die orbits 
of the heavenly bodies 

It seems that the human mind has first to construct 
forms mdependendy before we can find diem m things 
Kepler’s marvellous achievement is a particularly fine 
example of die truth that knowledge cannot spring 
from experience alone but only from the comparison 
of the inventions of the inrellecr with observ ed fact 

The Mechanics of Neu ion and their Influence on the 
Developn ent of Theoretical Ph)stcs 
It is just two hundred )ears ago smcc Newton dosed 
11s eyes for die last time It behoves us at such a 
moment to remember this brilliant gemus, who deter- 
mined the course of western thought, research and 
practice to an extent that nobody before or since hu 
nmc can touch Not only was he brilliant as an inventor 
of certain key methods, but he also had a unique com- 


maiid of the empirical material available m his day, 
and he was marvellously inventive as regards mathe- 
matical and ph) steal methods of proof m individual 
cases For all these reasons he deserves our deepest 
reverence The figure of Newton has, however, an 
even greater Importance than his genius warrants from 
the fact that destiny placed him at a turning-point m 
die history of die human intellect. To see this vividly, 
we have to remind ourselves that before Newton there 
existed no self-contained system of physical causality 
which was capable of representing any of the deeper 
features of the empirical world 

No doubt the great materialists of ancient Greece 
had insisted that all material events should be traced 
back to a strictly regular senes of atomic movements 
without admitting any living creature’s will as an 
independent cause And no doubt Descartes had in Ins 
own way taken up this quest agent But tt remained 
a bold ambmon, the problematical ideal of a school of 
philosophers Actual results of a kind to support die 
belief in die existence of a complete chain of physical 
causation hardly existed before Newton P P 

iT' 1 ob J cct %v f to answer thequesnon, Is there 
such a thing as a simple rule by which one can calculate 
tho movements of the heavenly bodies in our pUn et a“ 

— ■ TW ]™, gave , „ 

«nK ,rorn ,he *»ovenjea« « .they Werc 



complete answer to die question of how the planers 
move round the sun (the elliptical shape of the orbit, 
equal areas in equal times, die relation between the 
tnajor axes and the period of circulation round the 
sun) , but they did not satisfy the demand for causality 
They are three logically independent rules, rescaling 
no inner connection with each other. The third law 
canno r simply be transferred quanntatively to other 
central bodies than the sun (there is, for example, no 
relation between the rotator)' period ofa planet round the 
sun and that of a moon round its planet) The most 
important point, however, is this these law are con- 
cerned with the movement as a whole, and not with 
the question how the state of motion of a system gives rise 
to that which immediately follows it in time, they are, as we 
should say now, integral and not differential laws 

The differential law is the only form which com- 
pletely satisfies the modem physicist's demand for 
causality The clear concepnon of the differential law 
is one of Newton’s greatest intellectual achievements 
Ic was not merely the notion that was needed but 
also a mathematical formalism which existed in us rudi- 
ments but had to acquire a systematic form Newton 
found this also m the differcnnal and the integral 
calculus We need not consider the question here 
whether Newton hit upon the same mathematical 
methods mdependendy of Leibnitz or nor In any 
case it was absolutely necessary for New ton to perfect 
them, smee they alone could provide him with the 
means of expressing his ideas 

* Galileo had already made a considerable advance 
towards a knowledge of the law of motion He du- 
lire 'nrw xfi 'nanxci turi vi/t low *c K h/edws. falling 
freely in the gravitational field of the earth nameh, 

* 148 


that a mass, (more accurately, mass-point) which is 
unaffected by other masses, moves uniformly and in a 
straight line The vertical speed of a free body m die 
gravitational field increases uniformly with die time 
It may seem tD us to-day to be but a short step from 
Galileo's discoveries to Newton’s law of motion But 
it should be observed that both the above statements 
refer in their form to the motion as a whole, whereas 
Newton $ law of motion provides an answer to the 
question, How does the state of motion of a mass-point 
behave in an infinitely short tune under the influence of 
an external force? It was only by considermg what 
takes place during an infinitely short time (the differ- 
ential law) that Newton reached a formula which 
applies to all motion whatsoever He took the con- 
cept of force from staucs, which had already reached a 
high stage of development The connection between 
force ana acceleration was only made possible for him 
by the mtroduenon of the new concept of mass, which 
was supported, strange to say, by an illusory definition 
Wc arc so accustomed to-day to the creation of concepts 
corresponding to differentia! quonents diat we can 
hardly grasp now what a remarkable power of abstrac- 
tion it needed to reach die general differential law by a 
crossing of two frontiers, m the course of which the 
concept of mass had in addition to be invented 
But a causal conccpnon of motion was still far from 
being achieved For the motion was only determined 
by the equation of motion in cases where the force 
was given Inspired no doubt by the uniformity of 
planetary motions, Newton conceived die idea that 
the force operating on a mass was determined by the 
position of all masses situated at a sufficiendy sma }\ 
distance from the mass in question It was not tdl this 


connection was established that a completely causal 
conception of motion was achieved How Newton, 
starting from Keplers laws of planetary motion, per- 
formed this task for gravitation and so discovered that 
the kineac forces acting on the stars and gravit) were 
o f the same nature, is well known It is the combination 
of the Laws of Motion with the Law of Attraction 
which consntuces that marvellous edifice of thought 
which makes it possible to calculate the past and future 
states of a system from the state obtaining u one 
particular moment, in so far as the events fake place 
under the influence of the forces of gravity alone The 
logical completeness of Newton’s conceptual svsteni 
lay m this, that die only dungs that figure as causes of 
die acceleranon of the masses of a system are these 
mosses themselves 

On die strengdi of the basis here briefly sketched 
Newton succeeded in explaining die motions of the 
planets, moons and comets down to the smallest 
details, as well as die tides and die processional move- 
ment of the earth — a deductive achievement of unique 
magnificence The discover) that the cause of die 
monons of the heavenly bodies is identical with the 
gravity with winch we arc so familiar from everyday 
life must have been particularly impressive 

But the importance of Newton s achievement was 
not confined to the fact that it created a workable and 
logically satisfactory basis for the actual science of 
mechanics, up to the end of the nineteenth century it 
formed die programme of every worker in the field of 
theoretical physics All physical events were to be 
rraced back to masses which are subject to Newton s 
fews of motion The few of force suuply had to be 
widened and adapted to the type of event under con- 


sideration. Newton himself tried to apply this scheme 
to optics, assuming light to consist of inert corpuscles. 
Even the wave theory of light made use of Newton’s 
law of motion, after it had been applied to the mass of 
a continuum. Newton’s equations of motion were the 
sole basis of the kinetic theory of heat, which not only 
prepared people’s minds for the discovery of the law of 
the conservation of energy but also led to a theory ol 
gases which has been confirmed down to die last 
detail, and a more profound view of the nature of the 
second law of thermodynamics. The development of 
electricity and magnetism has proceeded right down to 
our own day along Newtonian lines (electrical and 
magnetic substance, forces acting at a distance). Even 
' the revolution in electrodynamics and optics brought 
about by Faraday and Clerk Maxwell, which formed 
the first great fundamental advance in theoretical 
physics since Newton, took place entirely under the 
argis of Nc won’s ideas Clerk Maxwell, Boltzmann 
and Lord Kelvin never weaned of tracing the electro- 
magnetic fields and their reciprocal dynamic actions 
back to die mcchamcal action of hypothetical con- 
tinuous media possessmg mass. As a result, however, 
of die hopelessness or at any rate the lack of success of 
those efforts, a gradual revolution m our fundamental 
notions has taken place since the end of the nineteenth 
century ; theoretical physics have outgrown the New- 
tonian frame which gave stability and intellectual 
guidance to science for nearly two hundred years. 

Ndwton’s fundamental principles were so satisfactory 
fwarcofview that the impetus to over- 
haul diem could only spring from die imperious 
demands of empirical fact. Before I go into this I 
must insist that Newton himself was better aware of 
151 - * 


the weaknesses inherent in his intellectual edifice than 
the generations of scientists which followed him. This 
fact has always roused my respectful admiration, and I 
should like, therefore, to dwell on it for a moment 
(i) In spite of die fact that Newton’s ambiaon to 
represent Jus system as necessarily conditioned by 
experience and to introduce the smallest possible 
number of concepts not directly referable to empirical 
objects is everywhere evident, he sets up the concept 
of absolute space and absolute arae, for which he has 
often been cnacised in recent yean But in this point 
Newton is particularly consistent He had realised that 
observable geometrical magnmidcs (discanccsofraareml 
points from one another) and dieir course in amc do 
not completely characterise monon in its physical 
aspects He proves this m the famous experiment with 
the rotating vessel of water Therefore, in addition to 
masses and their temporally vanablc distances, theremust 
be something else that determines motion That “sorre- 
tlnng’ he takes to be relation to “absolute space ’ He 
is aware that space must possess a kind of physical 
reality if Jus Jaws of monon are to base an) meaning, a 
reality of the same sort as material points and the 
intervals between them t 

The dear realisation of this reveals both Newtons 
wisdom and also a weak side to his thcor) For the 
logical structure of die latter would undoubted!) be 
more satisfactor) without this shadow') concept, w 
that case onl) tilings whose relations to perception ate 
perfectly clear (mass-points, distances) would enter 
into the laws , 

(a) The mrroduenon of forces a rang clirccth and 
instantaneously at a distance into the representation of 
the effects ofgravuy is not in keeping with the character 



of most of the processes familiar to us from everyday 
life Newton meets this objection by pointing to the 
fact tli at his law of reciprocal gravitation is not sup- 
posed to he a final explanation but a rule derived by 
induction from experience 

(3) Newton’s doctrine provided no explanation for 
the highly remarkable fact that the weight and the 
inertia of a body are determined by the same quantity 
(its mass) The remarkableness of this fact struck 
Newton himself 

None of these three points can rank as a logical 
objection to the theory In a sense they merely represent 
unsatisfied desires of die scientific spirit in its struggle 
for a complete and unitary penetration of natural 
events by thought 

Newton’s doctrine of monon, considered as the key 
idea bf die whole of theoreucal physics, received its 
first shock from Clerk Maxwell’s theory of electricity 
It became clear that the reciprocal actions between 
bodies due to electric and magnetic forces were effected, 
not by forces operating instantaneously at a distance, 
but by processes wlucli are propagated through space 
at a finite speed Faraday conceived a new sort of real 
physical entity, namely die 4 field,” in addition to the 
mass-point and its motion At first people tried, cling- 
ing to die mechanical mode of thought, to look upon 
it as a mechanical condiuon (motion or force) of a 
hypothetical medium b> which space was filled up 
(the edier) But when this interpretation refused to 
work m spite of the most obstinate efforts, people gradu- 
all> got used to the idea of regarding the “efeoro- 
nugneoc fidd" as a final irreducible comnraent of 
physical reality W c base H Hertz to thank for 
definitely freeing the conception of the field fiom all 


encumbrances derived from the Conceptual armour)' of 
mechanics, and H. A. Lorcntz for freeing it from a 
material substratum; according to the latter the only 
thing left to acr as a substratum for the field was physical 
- empty space (or ether), which even in the mechanics 
of Newton had not been destitute of all physical 
functions. By the time this point was reached, nobody 
any longer believed in immediate momentary action at 
a distance, not even in the sphere of gravitation, even 
though no field-theory of the latter had been clearly 
sketched out owing to lack of sufficient factual know- 
ledge. The development of the theory of the elect ro- 
magncnc field — once Newton's hypothesis of forces 
acting at a distance had been abandoned — led to the 
attempt to explain die Newtonian law of motion on 
electro-magnetic lines or alternatively to replace it by 
a more accurate one based on die field-theory. Even if 
these efforts did not meet with complete success, still 
the fundamental concepts of mechanics had ceased to 
be looked upon as fundamental constituents of die 
physical Universe. 

The theory of Clerk Maxwell and Lorentz led 
inevitably to die special theory of relativity, which 
ruled out the existence of forces acting at a distance, 
with the resulting destruction of the no don of absolute 
simultaneity. This theory made it clear that mass is 
not a constant quantity but depends on the cnerg)- 
content — is indeed equivalent to it. It also showed that 
Newton’s law of monon was only to be regarded as a 
limiting law valid for small velocities; in its place if 
put a new law of morion tn which the speed of light in' 
vacuo figures as the critical velocity. 

The general theory of relativity formed die bit 
step in the development of die programme of die field- 


theory. Quantitatively it modified Newtons theory 
only slightly, hut all the more profoundly for that 
qualitatively. Inertia, gravitation, and the metrical 
behaviour of bodies and clocks were -reduced to a 
single field quality, this field itself was again placed in . 
dependence on the bodies (generalisation of Newton s 
law of gravity or the field-law corresponding to it, as 
formulated by Poisson). Space and time were thereby 
divested not of their reality but of their causal absolute- 
ness (absoluteness affecting but not affected) which 
Newton had been compelled to ascribe to them in order 
to be able to give expression to the laws then known. 
The generalised law of inertia takes over the function 
of Newton’s law of motion. This short account is 
enough to show how die elements of the Newtonian 
theory passed over into the general theory of relativity, 
whereby the three defects above mentioned were over- % 
come. It looks as if the law of motion could be deduced ' 
from the field-law corresponding to the Newtonian law 
of force. Only when this goal has been completely reached 
will it be possible to talk about a pure field-theory. 

In a more formal -sense also Newton’s mechanics 
prepared the way for the field-theory. The application 
of Newton’s mechanics to continuously distributed 
masses led inevitably to the discovery and application 
of partial differential equations, which in their turn first 
provided the language for die laws of the field-theory. 
In this formal respect Newton’s conception of the 
differential law constitutes the first decisive step in the 
development which followed. 

The whole evolution of our ideas about die processes 
of nature, with which we have been concerned so far, 
might be regarded as an organic development of 
Newton s ideas. But while the process of perfecting 


die field-theory was still in full swing, the facts of heat- 
radiation, the spectra, radio-activity etc., revealed a 
limit to the serviceableness of the whole intellectual 
system which to-day still seems to us absolutely insuper- 
able in spite of immense successes at certain points. 
Many physicists maintain — and there are weighty 
arguments in their favour — that in the face of these 
facts -not merely the differential law but the law of 
causation itself— hitherto the fundamental postulate of 
all natural science — has collapsed. Even the possibility 
of a spatio-temporal construction, which can be 
unambiguously co-ordinated with physical events, is 
denied. That a mechanical system is permanently 
susceptible only of discrete energy-values or states — as 
experience, so to speak, directly shows— seems at first 
sight hardly deduable from a field-theory which 
operates with differential equations. The Dc Broglic- 
Schrpdwgcr method, which has in a certain sense die 
character of a field-theory, docs indeed deduce the 
discreteness of energy stares, in astonishing agreement 
with empirical fact, on the basis of differential equations 
operating with a kind of resonance-theory, but it has 
to do without a localisation of the mass-particlcs and 
without strictly causal laws. Who would presume 
to-day to dcade the question whether the law of 
causation and die differential law, diese ultimate 
premisses of die Newtonian view of nature, must 
definitely be given up i 

Clerk MaxwelPs on the Evolution of the lies 
of Physical Reality 

’Tut Wut5 Ttn an rmra’i '«xnVh vAepaAaA 
[ perceiving subject is die basis of all natural science. Since, 


however, seme perception only gives information ofthis 
external world or of “physical reality indirectly, we can 
only grasp die latter by speculative means. It follows 
from this that our notions ofpKysical Reality can never 
he final. We must always be ready to change these 
notions — that is to say, the axiomatic substructure of 
physics — in order to do justice to perceived facts in the 
most logically perfect way. Actually a glance at the 
development of physics shows that it has undergone 
far-reaching changes in the course of time. 

The greatest change in the axiomatic substructure of 
physics — in other words, of our conception of the 
structure of reality — since Newton laid the foundation 
of theoretical physics was brought about by Faraday’s 
and Clerk Maxwell’s work on electro-magnetic pheno- 
mena. We will try in what follows to make this 
clearer, keeping both earlier and later developments 
in sight. 

According to Newton’s system, physical reality is 
characterised by the concepts of time, space, material 
point, and force (=reciprocal action of material points). 
Physical events, in Newton’s view, are to be regarded 
as the motions, governed by fixed laws, of material 
points in space. The material point is our only mode of 
representing reality, when dealing with changes taking 
place in it. Perceptible bodies arc obviously responsible 
for the concept of the material point; people conceived 
it as an analogue of mobile bodies, stripping these of the 
characteristics of extension, form, orientation in space, 
and all “inward” qualities, leaving only inertia and 
•crndnmtm anh aaciing inc concept ol force. The 
material bodies, which had led psychologically to our 
formation of the concept of the “material point ” had 
now themselves to be regarded as systems of material 


points It should be noted that this theoretical scheme is 
m essence an atomistic and mechanistic one All happen- 
ings were to be interpreted purely mechanically — that is 
to say, simply as motions of material poults according 
to Newton’s law of motion 
The most unsatisfactory side of this system {apart 
from the difficulties involved in the concept of “absolute 
space” winch have been raised once more just recently) 
lay in its description of light, which NewtPn also con- 
ceived, m accordance with his system, as composed of 
material points Even at that time the question, What 
in that case becomes of the material points of which light 
is composed, when the light is absorbed i was alread) a 
burning one Moreover, it is unsatisfactory m any case 
to mto the dsscossum. mateml points Qt quite 
a different sort, which have to be postulated for the pur- 
pose of representing ponderable matter and light 
respectively Later on corpuscles of electuary were 
added to these, making a third kmd, again with com- 
pletely different characteristics It was further, a funda- 
mental weakness that the forces of reciprocal action, by 
which events are determined, had to be assumed hypo- 
thetically in a perfectly arbitrary way Yet this con- 
ception of the real accomplished much how came it 
that people felt themselves impelled to forsake it? 

In order to put his system into mathematical form at 
all, Newton had to devise the concept of differential 
quotients and propound the laws of monon in the form 
of total differential equations — perhaps the greatest 
advance in thought that a single individual was ever 
privileged to make Partial differential equations were 
not necessar) for dus purpose, nor did Newton make 
any systematic use of them , but they were nccessars for 
the formulation of the mechanics of deformable bodies, 



this is connected with the fact that m these problems the 
question of tow* bodies arc supposed to be constructed 
out of material points was of no importance to begin 

Thus the partial differential equation entered theo- 
retical physics as a handmaid, but has gradually become 
mistress This began in the nmeteenth century when 
the wave-theory of light established itself under the 
pressure of observed fact Light in empty space was 
explained as a matter of vibrations of the ether, and it 
seemed idle at that stage, of course, to look upon the 
latter as a conglomeration of material points Here for 
the first time the partial differcnual equation appeared 
as the natural expression of the primary realities of 
physics In a particular department o f theo rencal physics 
the continuous field thus appeared side by side with the 
material point as the representative of physical reality 
This dualism remains even to-day, disturbing as it must 
be to every orderly mind 

If the idea of physical reality had ceased to be purely 
atomic, it still remained for the time being purely 
mechanistic, people still tried to explam all events m 
terms of the motiou of inert masses, indeed no other 

way of looking at things seemed conceivable Then 
came the great change, which will be associated for all 
time with the names of Faraday, Clerk Maxwell, and 
Hertz. The hon’s share in this revolution fell to Clerk 
Max^\ ell He showed that the whole of what was then 
known about light and electro-magnetic phenomena 
was expressed in his well-known double system of 
' differential equations, m which the electric and the man 
netic fields appear as the dependent variables Maxwell 

m& d cX°n* ^ ^ th - — by 

1 59 


But he made use of several such constructions at the 
same. tunc and took none of them really senously, so 
that the equations alone appeared as the essential thing 
and the strength of die fields as the ultimate entities, not 
to be reduced to anything else By the turn of die 
century the conception of the electro-magnetic field as 
an ultimate entity had been generally accepted and 
serious dunken had abandoned the belief in thcjustifica- 
ti6n, or die possibility', of a mechanical explanation of 
Clerk Maxwell's equations Before long they were, on 
the contrary , actually trying to explain material points 
and their inerna on field-theory lines with die help of 
Maxwell’s theory, an attempt which did not, however, 
meet with complete success 
Neglecting the important individual results which 
Clerk Maxwell’s life-work produced in several main 
departments of physics, and concentrating on the 
changes wrought by him in our concepnon of the nature 
of physical reality, we may say tins — Before Clerk 
Maxwell physical reality was conceived — in so far as it 
was mtended to represent events m nature — as made up 
of material points, whose changes consist exclusively of 
motions which arc subject to partial differential equa- 
tions After Maxwell they conceived physical reality as_ 
represented by conrinuSus fieldsT~not mechanically _ 
explicable, which ^re subject to partial - differential 
'equations Tins change in the conception of reality is 
the most profound and fruitful one that has come to 
physics since Newton , but it has at die same time to be 
admitted that die programme his not yet been com- 
pletely earned out by any means The successful systems 
of physics which hai e been cvolv cd smee rather represent 
compromises between diesc two schemes, which for 
that very reason bear a provisional, logically incomplete 


character, although they may have achieved great 
advances in certain particulars. 

The first of these that calls for mention is Lorentz* s 
the or)' of electrons, in which the field and the electrical 
corpuscles appear side by side as elements of equal value 
for die comprehension of reality. Next come die 
special and general theories of relativity, which, though 
based entirely on ideas connected widi die ficld-dieory, 

' have so far been unable to avoid the independent intro- 
duction of material points and total differential equations. 

The last and most successful creadon of theoretical 
physics, namely quantum-mechanics, differs funda- 
mentally from both die schemes which we will for die 
sake of brevity call die Newtonian and the Maxwellian. 
For the quantities which figure in its laws make no 
claim to describe physical reality itself, but only die 
probabilities of the occurrence of a physical reality that 
we have in view. Dirac, to whom, m my opimon, we 
owe the most logically complete exposition of this 
theory, nghdy points out that it would probably be 
difficult, for example, to give a dicorctical description of 
a photon such as would give enough information to 
enable one to decide will pass a polanser 
placed (obliquely) m its way or nor. 

I am still inclined to the view that physicists will not 
" m die long run content themselves with that sort of 
indirect description of the real, even if die dieory can 
eventually be adapted to the postulate of general rela- 
tivity m a satisfactory manner. We shall then, I feel 
sure, have to return to the attempt to carry’ out die pro- 
gramme which may properly be described as the. Max- 
wellian— namely, the description of physical reality in 
terms of fields which satisfy partial differential equations 
without singularities 
* 161 


Niels Bohr 

When a later generation comes to write the history of 
the progress made in ph) sics m our tjme, it will have 
to connect one of the most important advances ever 
made m our knowledge of the nature of the atom with 
the name of Niels Bohr It was alrcad) known that 
classical mechanics break down in relation to the ulti- 
mate constituents of matter, also that atoms consist of 
positively charged nuclei which are surrounded by a 
layer of atoms of relatively loose texture But the 
structure of the spectra, which was to a large extent 
known empincall), was so profoundly different from 
what was to be expected on our older theories that 
nobody could find a convincing theoretical interpreta- 
tion of the observed uniformities Thereupon Bohr in 
the year 1913 devised an interpretation of the simplest 
spectra on quantum-theory lines, for which he in a 
short tunc produced such a mass of quantitative confir- 
mation that the boldl) selected hypothetical basis ofhis 
spcculanons soon became a mainstay for the ph) sics of 
the atom Although less than ten >ears have passed 
since Bohr s first discovery, the system conceived in its 
main features and large!) worked out by him already 
dominates both physics and chemistry so completely 
that all earlier systems seem to the expert to date from 
a long-vanished age The theories of X-ra) spectra, of 
visible spectra, and of the periodic s) stem of the elements 
are primarily based on the ideas of Bohr What is so 
marvellously attracm e about Bohr as a scientific thinker 
is lus rare blend of boldness and caution, seldom has 
anyone possessed such an intuitive grasp of hidden 
things combined with such a strong critical sense. With 
all his knowledge of the details, his eye is immovably 


fixed on the underlying principle He is unquestionably 
one of the greatest discov crcrs of our age in the scientific 

On the Theory of Relativity 
An Address in London 

It is a particular pleasure t<5 me to have the privilege 
of speaking in the capital of the country from which 
the most important fundamental notions of theoretical 
physics have issued I am thinking of the theory of 
mass motion and gravitation which Newton gave us 
and of the concept of the electro-magnetic field, by 
means of which Faraday and Clerk Maxwell put physics 
on a new basis The theory of relativity may indeed be 
said to have put a sort of finishing touch to the mighty 
intellectual edifice of Maxwell and Lorentz, inasmuch 

as it seeks to extend field-physics to all phenomena, 
gravitation included 

Turning to the theory of relativity itself, l am anxious 
to draw attention to the fact that this theory is not 
speculative in origin, it owes its invennon entirely to 
the desire to make physical theory fit observed fact as 
well as possible "W e have here no revolutionary act but 
the natural continuation of a line that can be traced 
through centuries The abandonment of a certain con- 
cept connected with space, time and motion hitherto 
treated as fundamental must not be regarded as arbitrary 
but only as conditioned by observed facts 
The law of the constant velocity of light m empty 
space, wnicn Wbcen confirmed by the development of 
electro-dynamics and optics, and ' 
legitimacy of all inertial systems 
relativity), which was proved in a 

— -V vi*. uic CLJUaj 

(special principle of 
paracularh incisive 


manner b> Michclson s famous experiment, between 
them made it necessary, m the first place, that the concept 
of nmc sliould be made relative, each inertia! system 
being given its own special nmc As this notion was 
developed it became clear thar the connection between 
immediate experience on one side and co-ordinates and 
time on the other had hitherto not been thought out 
with sufficient precision It is m general one of the 
essential features of the theory of relativity that it is at 
pains to work out the relations between general con- 
cepts and empirical facts more precisely The funda- 
mental principle here is that the justification for a phvsi- 
cal concept hes cxclusn cly in its clear and unambiguous 
relation to facts that can be experienced 
According to the special theory of relativit), spanal 
co-ordinates and time still have an absolute character in 
so far as they are directly measurable b) stationary clocks 
and bodies But they arc relame in so far as they 
depend on the state of motion of the selected incmal 
system According to the special theory of relativit) 
the four-dimensional continuum formed by the union 
of space and time retains the absolute character which 
according to the earlier theory, belonged to both space 
and time separately (Mihkowsla) The influence of 
motion (relative to the co-ordinate system) on the form 
of bodies and on the motion of clocks, also the equiva- 
lence of energy and inert mass follow from the inter- 
pretation of co-ordinates and ome as products of 

The general theory of relativity ow cs its existence in 
the first place to the empirical fact of the numerical 
equaht) of the inertial and gravitational mass of bodies 
for which fundamental fact classical mechanics provided 
no interpretation Such an interpretation is arrived at 


by an extension of the principle of relativity to co- 
ordinate systems accelerated relatively to one another 
The introduction of co-ordinate systems accelerated 
relatively to inertial systems involves the appearance of 
gravitational fields relative to the latter As a result of 
this, the general theory of relativity, which is based on 
the equality of inertia and weight, provides a theory of 
the gravitational field 

The introduction of co-ordmatc systems accelerated 
relatively to each other as equally legitimate systems, 
such as they appear conditioned by the identity of 
inertia and w eight, leads, in conjunction with the results 
of die special theory of relativity, to the conclusion that 
the laws governing the occupation of space by solid 
bodies, when gravitational fields arc present, do not 
correspond to the laws of Euclidean geometry An 
analogous result follow's from the motion of clocks 
This brings us to the necessity for yet anodicr generalisa- 
tion of the theory of space and time, because the direct 
interpretation of space and time co-ordinates by means 
of measurements obtamable with measuring rods and 
clocks now breaks down That generalisation of metric, 
which had already been accomplished m the sphere of 
pure mathematics by the researches of Gauss and Rjc- 
mann, is essentially based on the fact that the metric of 
the special theory of relativity can still claim validity for 
small areas in the general case too 
The process of development here sketched strips die 
space- time co-ordinates of all independent reality The 
metrically real is now only given through the combina- 
tion of die space-time co-ordinates with the mathemati- 
cal quantities which describe the gravitational field 
There is yet mother factor underlying the evolution 
of the general theory of relativity As Ernst Mach 


insistently pointed out, the Newtonian theory is unsarn- 
factory in die following respect — If one considers 
motion from the purely descriptive, not from the causal, 
point of view, it only exists as relative motion of things 
with respect to one another But the acceleration winch 
figures in Newton’s equations of motion is unintelligible 
if one starts with die concept of relative motion It 
compelled Newton to invent a physical space in relation 
to which acceleration was supposed to exist This intro- 
duction ad hoc of the concept of absolute space, while 
logically unexceptionable, nevertheless seems unsatis- 
factory Hence the attempt to alter the mechanical 
equations in such a way that? the inertia of bodies is 
traced bach to relative motion on their part not as 
against absolute space but as against the totality of other 
ponderable bodies In the state of knowledge then 
existing his attempt was bound to fail 
The posing of the problem seems, however, entirely 
reasonable This line of argument imposes itself with 
considerably enhanced force in relation to the general 
theory of relativity, since, according to that theory, the 
physical properties of space are affected by ponderable 
matter In my opinion, the general theory of relativity 
can only Solve tins problem satisfactorily if it regards 
the world as spatially seI£endosed The mathematical 
results of the theory force one to this view, if one 
believes that the mean density of ponderable matter m 
the world possesses some ultimare value, however small 

What is the Theory of Relativity* * 

I gladly accede to the request of your colleague to 
write somednng for The Times on relativity After the 
lamentable breakdown of the old acme intercourse 
1 66 


mulatcd criteria which the separate processes or the 
theoretical representations of them have to satisfy Thus 
the science of thermodynamics seeks by analytical means 
to deduce necessary' connections, which separate events 
have to satisfy, from the universally experienced fact 
that perpetual motion is impossible 
The advantages of the construcuve theory are com- 
pleteness, adaptability and clearness, those of the prin- 
ciple-theory are logical perfection and security of the 

The theory of relativity belongs to the latter class 
In order to grasp its nature, one needs first of all to 
become acquainted with the principles on which it is 
based Before I go into these, however, I must observe 
that the theory of relativity resembles a budding con- 
sisting of two separate storeys, the special theory and 
the general theory The speaal theory, on which the 
general theory rests, applies to all ph>sica! phenomena 
with the exception of gravitation , the general theory 
provides the law of gravitation and its relations to the 
other forces of nature 

It has, of course, been known since 'the days of the 
ancient Greeks that in order to describe the movement 
of a body, a second body is needed to which the move- 
ment of the first is referred The movement of a 
vehicle is considered m reference to the earth’s surface, 
that of a planet to the totality of the visible fixed stars 
In physics the body to which events are spatially referred 
is called the co-ordinate system The laws of the 
mechanics of Galdeo and Newton, for instance, can only 
be formulated with the aid of a co-ordinate system 
The state of motion of the co-ordinate system may not, 
however, be arbitrarily chosen, if the laws of mechanics 
are tp be valid (it must be free from rotation and accclera- 


non) A co-ordinate system which is admitted in 
mechanics is called an "inertial system The state of 
mouon of an inertial system is according to mechanics 
not one that is determined unambiguously by nature 
On the contrary, the following definiaon holds good — 
a co-ordinate S) stem that is moving uniformly and in a 
straight line relanvcly to an inertial system is likewise an 
menial system By the “special principle of rclaavity 
is meant the generalisaaon of tins definition to include 
any natural event whatever thus, ever) universal law 
of nature which is valid in relation to a co-ordinate 
system C, must also be valid, as it stands, in relation to 
a co-ordinate system C 1 , which is in uniform translatory 
monon relanvcly to C 

The second principle, on which the special theory of 
relauvity rests, is the “principle of the constant velocity 
of light in vacuo ” This principle asserts that light in 
vacuo always has a definite velocity of propagauon, 
independent of the state of moaon of the observer or of 
the source of light The confidence which physicists 
place m this principle springs from the successes achieved 
by die electro-dynamics of Clerk Maxwell and Lorentz. 

Both the abovc-menuoned principles are powerfull) 
supported by experience, but appear not to be logically 
reconcilable The special theory of relauvity finally 
succeeded in reconciling them logically by a modifica- 
uon of kinemaucs — i e , of the doctrine of the laws 
relating to space and ume (from the point of view of 
physics) It became clear that to speak of die simul- 
tonaty °f two events had no meaning except m rclanon 
* to-oriuiate system, and that the shape of 
measurmg devices and the speed at which clods move 



incma of a body arc controlled by the same constant 
(Equality of inertial and gravitational mass ) Imagine a 
co-ordinate system which is rotanng uniformly with 
respect to an inertial system in the Newtonian manner 
The centrifugal forces which manifest themselves in 
relation to tins system must, according to Newton's 
teaching, be regarded as effects of merna But these 
centrifugal forces are, exactly like the forces of gravity, 
proportional to the masses of the bodies Ought it nor 
to be possible in this case to regard the co-ordinate sys- 
tem as stationary and the centrifugal forces as gravita- 
tional forces } This seems the obvious view, but classical 
mechanics forbid it 

This hasty consideration suggests that a general 
theory of relativity must supply d e laws of gravitanon, 
and the consistent following-up of the idea has justified 
our hopes 

But the path was thornier than one might suppose, 
because it demanded the abandonment of Euclidean 
geometry That is to say, the laws according to which 
fixed bodies may be arranged m space do not com- 
pletely accord with the spatial laws attributed to bodies 
by Euclidean geometry Tins is what we mean when 
we talk of die “curvature of space ” The fundamental 
concepts of the “straight hne,’ die “plane” etc thereby 
lose their precise significance in physics 
In the general theory of relativity the doctrine of 
space and time, or kinemancs, no longer figures as a 
fundamental independent of the rest of physics The 
geometrical behaviour of bodies and the motion of 
docks rather depend on gravitanonal fields, which in 
dieir turn are produced by matter 
The new theory of gravitation diverges considerably, 
as regards principles, from Newton’s theory But its 


practical results agree so nearly with those of Newton’s 
theory that it is difficult to find criteria for distinguishing 
them which are accessible to experience Such have 
been discovered so far — 

(1 ) *In the revolution of the ellipses of the planetary 
orbits round the sun (confirmed in the case ofMcrcury) 

(2) In the curving of light rays by the action of gravi- 
tational fields (confirmed by the English photographs 
of eclipses) 

(3) In a displacement of the spectral lines towards the 
red end of the spectrum in the case of light transmitted 
to us from stars of considerable magnitude (uncon- 
firmed so far) 1 

The chief attraction of the theory lies in its logical 
completeness If a single one of the conclusions drawn 
from it proves wrong, it mtut be given up , to modify 
it without destroying the whole structure seems ro be 

Let no one suppose, however, that the mighty work 
of Newton can really be superseded by this or any other 
theory His great and luad ideas will retain their unique 
significance for all time as the foundation of otir whole 
modem conceptual structure m the sphere of natural 

Addendum Some ofthe statements m yourpaper con- 
cerning mv life and person owe their origin to the hi cl) 
imagination of the writer Here is )ct another applica- 
tion of the principle of relativity for the delectation of 
the reader — To-day I am described in Germany as a 
"German savant," and in England as a “Swiss Jew 
Should it ever be my fate to be represented as a betc 
noire , I should, on the contrary, become a "Swiss Jew 

* Editor’* Note This criterion has also been confirmed in the meantime 


for the Germans and a “German savant” for the 

The Problem of Space, Ether, and the Field m Physics 

Scientific thought is a development of pre-saennfic 
thought As the concept of space was already funda- 
mental in the latter, we must begin with the concept ot 
space in pre-scicnufic thought There are two ways or 
regardmg concepts, both of which are necessary to 
understanding The first is that of logical analysis It 
answers the question, How do concepts and judgments 
depend on each other? In answering it we are on com- 
paratively safe ground It is the security by whic 1 we 
are so much impressed m mathematics But this secu- 
rity is purchased at the price of emptiness of content 
Concepts can only acquire content when they are con- 
nected, however indirectly, with sensible experience 
But no lo gical investi g ation can revg aLthisconnection^ 
lfcanpriTy he expenencedT~ And yet it is this connection 
"tHaTdetemunes the cognitive value of systems of con- 

Take an example Suppose an archeologist belonging 
to a later culture finds a text-book of Euclidean geo- 
metry without diagrams He will discover how the 
words “point,” “straight line,” “plane, are used m the 
propositions He will also see how the latter are deduced 
from each other He will even be able to frame new 
propositions according to the known rules But the 
framing of these propositions will remain an empty 
word-game for him, as long as “point, straight line, 
“plane etc “convey nothing” to lum Only when they 
do convey something will geometry possess any real 
content for him The same will be true of analytical 


Now as regards the concept of space, this seems to 
presuppose the concept of the sohd object. The nature 
of the complexes and sense-impressions whvh are prob- 
ably responsible for that concept has ofi-n been 
described The correspondence between certain visual 
and tactile impressions, the fact that they can be con- 
tinuously followed out through time, and that the -1 
impressions can be repeated at any moment (taste, sight), 
arc some of those characteristics Once the concept of 
the solid object is formed in connection with the 
experiences just mentioned — which concept by no 
means presupposes that of space or spatial relation the 
desire to get an intellectual grasp of the relations of such 
sohd bodies is bound to give rise to concepts which 
correspond to their spatial relations Two solid objects 
may touch one another or be distant from one another 
In the latter case, a third body can be inserted between 
them without altering them in any way , m the former 
not These spatial relations arc obviously real in the 
same sense as the bodies themselves If two bodies are 
of equal value for the filling of one such interval, they 
will also prove of equal value for the filling of other 
intervals The interval is thus shown to be independent 
of the selection of any special body to fill it, the same 
is universally true of spatial relations It is plain that 
this independence, which is a principal condition of the 
usefulness of framing purely geometrical concepts, is 
not necessanly a prion In my opinion, this concept of 
the interval, detached as it is from die selection of any 
special body to occupy it, is the starting-point of the 
whole concept of space 

Considered, then, from the point of view of sense 
experience, die development of the concept of space 
seems, after diese bnet mdicauons, to conform to the 


mechanics, and indeed of any exposition of the logically 
deductive sciences. * 

What docs this talk of "straight line,*’ "point, 1 ' 
"intersection" etc. ‘"conveying something to one" 
meant It means that one can point to the parts of 
sensible experience to which those words refer. This 
extra-logical problem is the essential problem, which 
the archxologist will only be able to solve intuitively, 
by examining his experience and seeing if he can dis- 
cover anything which corresponds to those primary 
terms of the theory and the axioms laid down for them. 
Only in this sense can die question of the nature of a 
conceptually presented entity be reasonably raised. 

With our pre-scicntific concepts we are. very much 
in the position of our archarologist in regard to 'the 
ontological problem. We have, so to speak, forgotten 
what features in the world of experience caused us to 
frame those concepts, and we have great difficulty in 
representing the world of experience to ourselves with- 
out the spectacles of the old-established conceptual 
interpretation. There is the furdier difficulty that our 
language is compelled to work with words which are 
inseparably connected widi those primitive concepts. 
These are the obsrades which confront us when we try 
to describe the essential, nature of the p re-scientific con- 
cept of space. 

One remark about concepts in general, before we 
turn to the problem of space - concepts have reference 
to sensible experience, bur they are never, in a logical 
sense, deduable from them. For tins reason I have never 
been able to understand the quest of the a priori in the 
Kano an sense. In any ontological question, the only 
possibleprocedure is to seek out those characteristics m the 
complex of sense experiences to which die conccptsrcfcr. 



Now as regards the concept of space this seems to 
presuppose the concept of the solid obj-ct. The nature 
of the complexes and sense-impressions whvh arc prob- 
ably responsible for that concept has ofi-n been 
described The correspondence between certain visual 
and tactile impressions, the fact that they can be con- 
tinuously followed out through time, and that thc v 
impressions can be repeated at any moment (taste, sight), 
are some of those charactensncs Once die concept of 
the solid object is formed m connection with the 
experiences just mentioned — which concept by no 
means presupposes that of space or spatial relation — the 
desire to get an intellectual grasp of the relations of such 
solid bodies is bound to give rise to concepts which 
correspond to their spanal relations Two solid objects 
may touch one another or be distant from one another 
In die latter case, a third body can be inserted between 
them without altering them m any way , in the former 
not These spanal relations are obviously real in the 
same sense as the bodies themselves If two bodies arc 
of equal value for the filling of one such interval, diey 
will also prove of equal value for the filling of other 
intervals The interval is thus shown to be independent 
of the selection of any special body to fill it , the same 
is universally true of spatial relaoons It is plain that 
this independence, which is a principal condition of the 
usefulness of framing purely geometrical concepts, is 
not necessarily a prion In my opinion, this concept of 
the interval, detached as it is from the selection or any 
special body to occupy it, is the starting-point of the 
•whole concept of space 

Considered, then, from the point of view of sense 
expenence, the development of the concept of space 
seems, after these bnef indications, to conform to the 


following schema— solid body, spatial relations of solid 
bodies, interval, space Looked-at in this way, space 
appears as .something real in the same sense as solid 
bodies ■* ~ • 

^ It is clear tliat the concept of space as a real thing 
already existed in the extra-scientific conceptual world 
Euclid's mathematics, however, knew nothing of this 
concept as such , they confined themselves to the con- 
cepts of the object, and the spanal rclanons between 
objects The. point, the plane, the straight line, length, 
are solid objects idealised All spatial relations are 
reduced to those of contact (the intersection of straight 
lines and planes, points lying on straight lines, ere.) 
Space as a continuum does not figure m the conceptual 
system at all This concept was first introduced by 
Descartes, when he described the pomt-m-space bv its 
co-ordinates Here for the first time geometrical 
figures appear, up to a paint, as parts of infinite space, 
which is conceived as a three-dimensional continuum 
The grear superiority of the Cartesian treatment of 
space is by no means confined to the fact that it applies 
analysis to the purposes of geometry The main point 
seems rather to be this — The geometry of the Greeks 
prefers certain figures (the straight hne, die plane) in 
geometrical descriptions, other figures (e g , the clhpse) 
are only accessible to it because it constructs or defines 
them with die help of the point, the straight line aiid the 
plane In the Cartesian treatment on the other hand, all 
surfaces are, in principle, equally represented, without 
any arbitrary preference for linear figures in die con- 
struction of geometry 

In so far as geometry is conceived as the science of 
laws go\ eming the mutual relations of practically rigid 
bodies m space, it is to be regarded as the oldest branch 



of physics. This science was able, as 1 have already 
observed, to dispense with the concept of space as 
such; the ideal corporeal forms — point, straight line, 
plane, length— being sufficient for its needs. On the 
other hand, space as a whole, as conceived by Descartes, 
was absolutely necessary to Newtonian physics. For 
dynamics cannot manage with the concepts of the mass- 
point and the (temporally variable) distance between 
* mass-points, alone. In Newton’s equations of motion 
the concept of acceleration plays a fundamental part, 
which cannot be defmed by the temporally variable 
intervals between points alone. Newton’s acceleration 
is only thinkable or definable in relation to space as a 
whole. Thus to the geometrical reality of the concept 
of space a new inertia-determining function of space 
was added. When Newton described space as absolute, 
he no doubt meant this real significance of space, which 
made k necessary for him to attribute to it a quite definite 
state of motion, which yet did not appear to be fully 
determined by the phenomena of mechanics. This 
space was conceived as absolute in another sense also ; 
its inertia-determining effect was conceived as autono- 
mous, i.e., not to be influenced by any physical circum- 
stance whatever ; it affected masses, but nothing affected 

And yet in tire minds of physicists space remained 
until the most recent time simply the passive container 
of aU events, playing no pan in physical happenings 
itself. Thought only began to rake a new turn with 
the wave theory of light and the theory of the electro- 
magnetic field of Faraday and Clerk Maxwell. It 
became clear that there existed in free space conditions 
which propagated themselves in waves, as well as 
.localised fields which were able to exert force on clec- 



meal masses or magnetic poles brought to the spot 
Since it -would have seemed utterly absurd to the 
physicists of the nineteenth century to attribute physical 
functions or states to space itself, they in\ ented a medium 
pervading the -whole of space, on the model of ponder- 
able matter — the ether, which was supposed to act as a 
vehicle for electro-magnetic phenomena, and hence for 
those of light also The states of this medium, imagined 
as constituting the electro-magnetic fields, were at first 
thought of mechanically, on the model of the clastic 
deformations of rigid bodies But this mechanical 
theory of the edier was never quire successful, and so the 
idea of a closer explanation of the nature of the cthcnc 
fields was given up The ether thus became a kind of 
matter whose only function was to act is a substratum 
for electrical fields which were by their very nature not 
further analvsable The picture was, then, as follows — 
Space is filled by the ether, in which the material 
corpuscles or atoms of ponderable matter swim, the 
atomic structure of the latter had been securely estab- 
lished by the turn of the century 
Smcc the reciprocal action of bodies was supposed to 
be accomplished through fields, there had also to be a 

f raw rational field in the ether, whose field-law had, 
oweser, assumed no clear form at that time The 
ether was only accepted as the seat of all operations of 
force which make themselves effective across space 
Since it had been realised that electrical masses in 
motion produce a magnetic field, whose energy acted as 
a model for inertia, inertia also appeared as a field- 
acaon localised in the ether 
The mechanical properties of the ether were at first a 
mystery Then came H A Lorenrzs great iistmcr/ 

All the phenomena of electro-magnetism then known 



could be explained on the basis of two assumptions that 
the ether is firmly fixed in space — that is to Say, unable 
to move at all , and that electricity is firmly lodged in 
the mobile elementary parades To-dav his discovery 
may be expressed as follows — Physical space and the 
ether are only different terms for the same thing , fields 
are physical condmons of space For if no particular 
state of motion can be ascribed to the ether, there does 
not seem to be any ground for introducing it as an 
entity of a special sort alongside of space But the 
physicists were still far removed from such a way of 
thinking , space was still, for them, a rigid, homogeneous 
something, susceptible of no change or condmons 
Only the genius of Riemaim, solitary and uncompre- 
hended, had already won its way by the middle of last 
century to a new concepuon of space, in which it was 
deprived of its rigidity and its power to take part in 
physical events recognised as possible This intellectual 
achievement commands our admirauon all the more 
for having preceded Faraday’s and Clerk Maxwell’s 
field-theory of electricity Then came the special theory 
of relativity with its recognition of the physical equiva- 
lence of all inertial systems The inseparableness of 
time and space emerged m connecaon with electrodyna- 
mics, or die law of the propagation of light Hitherto 
it had been silently assumed that the four-dimensional 
continuum of events could be split up into time and 
space in an objective manner — le, that an absolute* 
significance attached to the “now” in the world of 
events With the discovery of the relanviry of simul- 
taneity, space and time were merged in a single con-, 
tinuum. in the same way as the three dimensions of 
space had been before Phvsical space was thus in- 
creased to a four-dimensional space which also included 


the. dimension of time The four-dimensional space of 
the jpecial theory of relativity is just as rigid and abso- 
lute as Newton’s space 

The thcoty of relativity admirably exemplifies the 
fundamental character of die modem development of 
theoretical science The hypotheses with which it starts 
become steadily more abstract and remote from experi- 
ence On die other hand it gets nearer to die grand 
aim of all science, which is to cover the greatest possible 
number of'emp meal facts by logical deduction from the 
smallest possible number of hypotheses or axioms 
Meanwhile the tram of thought leading from the axioms 
to the empirical facts or verifiable consequences gets 
steadily longer and more subtle The theoretical scientist 
is compelled in an increasing degree to he guided by 
purely mathematical, formal considerauons in his 
search for a theory, because the physical experience of 
the expen mentor cannot lift him into die regions of 
highest abstraction The predominantly inductive 
methods appropriate to die youdi of science are giving 
place to tentative deduction Such a theoretical struc- 
ture needs to be very thoroughly elaborated before it 
can lead to conclusions which can be compared with 
expenence Here, too the observed fact is undoubtedly 
the supreme arbiter, but it cannot pronounce sentence 
until the wide chasm separating die axioms from dieir 
verifiable consequences has been bridged by much 
intense hard thinlang The theorist has to set about this 
Herculean task m the clear consciousness that his efforts 
may only be destined to deal the death-blow to his 
theory The dieorist who undertakes such a labour 
should not be carped at as fanciful , on the contrary, 
he should be encouraged to give free reign to his fancy 
for there is no other way to die goal His is no idle day- 


dreaming, but a search for the logically simplest possi- 
bilities and their consequences This plea was needed m 
order to make the hearer or reader more ready to follow 
the ensuing train of ideas with attention , it is the line of 
thought which has led from die special to the general 
theory of relativity and dience to its latest offshoot, the 
unitary field-theor} In this exposinon the use of 
madiemancal symbols cannot be avoided 
We start with die special dieory of relativity This 
theory is still based directly on an empirical law, that of 
the constant velocity of light Let P be a pomt m 
empty space, P' one separated from it by a length do 
and infinitel) near to it Let a flash of light be emitted 
from P at a time t and reach P' at a time t -f- dt Then 

do* = c*dt* 

f dx, dx, dx, arc the orthogonal projections of do, 
and die imaginary tune co-ordinate V-i ct = x. is 
introduced, dicn the above-mentioned law of the con- 
stancy of die propagation of light takes the form 
ds* = dx,* + dx,* + dx,* -f dx.* = o 
Since this formula expresses a real situation, we may 
attnbme a real meaning to the quannty ds even sup- 
posing the neighbouring points of the fdur-dimcnsional 
ZT.T are , selcctcd m such a wa Y ds belong- 

nectcd SU r h u mCmc 13 calkd „ con _ 

»^c Th = of»ch a 

lem to the D osmrT°,“ lc 0 na ' 1 UUm, 5 full y c< l ul ™- 
metry The ^ ie 1X101113 °f Euclidean geo- 

^ ThC defimn S ^nation of the memo is dius 


nothing but the Pythagorean theorem applied to the 
differentials of the co-ordmatcs 

Such alteration of the co-ordmatcs (by transforma- 
tion) is permitted in the special theory of rclanvit), 
smee in the new co-ordmatcs too the magnitude ds* 
(fundamental invariant) is expressed In the new dif- 
ferentials of the co-ordinates by the sum of the squares 
Such transformations arc called Lorentz transformations 

The heuristic method of the special theory of rela- 
tivity is characterised by the following principle — Onlv 
those equations are admissible as an expression of natural 
laws which do not change their form when the co- 
ordinates are changed by means of a Lorentz transforma- 
tion (co-variance of equations m rclanon to Lorentz 

This method led to the discovery of die necessary 
connection between impulse and energy, the strength 
of an clectnc and a magnetic field electrostatic and 
elcctro-d) nainic forces inert mass and energy, and the 
number of independent concepts and fundamental 
equations was thereby reduced 
This method pointed beyond itself Is it true that the 
equations which express natural laws are co-variant in 
rclanon to Lorentz transformanons onl) and not in 
relanon to other transformations t Well formulated in 
that way die question really means nothing, since e\ cry 
system of equations can be expressed ui general co- 
ordinates Wc must ask. Ate not die laws of nature 
so constituted that dicy rcccne no real simplification 
through the choice of any one particular set of co-ordi- 
nates t . 

We will only mention in passing diat our empire*! 
principle of die equality of men ana* Aravy m**** 
prompts us to answer tins question in the affirmative 


If we elevate the equivalence of all co-ordinate systems 
for the formulation of natural laws into a principle, we 
amve at the general theory of relativity, provided we 
stick to the law of the constant velocity of light or to 
the hypothesis of the objective significance of die 
Euclidean metric at least for infinitely small portions of 
four-dimensional space 

This means diat for finite regtons of space the exist- 
ence (significant for physics) of a general Riennnman 
metric is presupposed according to the formula 

ds* = ^ ^ 


whereby the summation is to be extended to all index 
combinations from 1 1 to 44 
/The structure of such a space differs absolutely 
radically in one respect from diat of a Euclidean space 
The coefficients^ arc for die tune being any functions 
whatever of the co-ordinates xi to x*, and the structure 
of the space is not really determmed until diese functions 
£nv are really known It is only determmed more 
closely by specifying laws which the metrical field of 
the^ v satisfies On physical grounds this gave rise to 
the conviction that the metrical field was at the same 
time die gravitational field 
Since the gravitational field is determined b) the 
configuration of masses and changes with it, the geo- 
metric structure of this space is also dependent on 
physical factors Thus according to this theory space is 
—exactly as Riemann guessed— no longer absolute , its 
structure depends on physical influences Physical geo- 
metry is no longer an isolated self-contained science like 
the geometry of Euclid 

The problem of gravitation was thus reduced to a 


mathematical problem it was required to find the 
simplest fundamental equations "which are co-variant in 
relation to any transformation of co-ordinates whatever 
I Will not speak here of die way this theory has been 
confirmed by experience, but explain at once why 
Theory could not rest permanend) satisfied with this 
success Gravitation had indeed been traced to the 
structure of space, but besides the gravitational field 
there is also die electro-magnetic field Tins had, to 
begin with, to be mtroduced into the theory as an 
entity independent of gran cation Additional terms 
which took account of the existence of the electro- 
magnetic field had to be included in die fundamental 
equations for the field But die idea that there were two 
structures of space independent of each odicr, the 
metric-gravitational and the elcctro-magnenC, was in- 
tolerable to the theoretical spirit We arc forced to the 
belief that both sorts of field must correspond to a 
unified structure of space 

The "unitary ficld-dieor) " which represents itself as 
a mathematically independent extension of the general 
theory of rclamit), attempts to fulfil this last postulate 
of the field theory The formal problem should be put 
as follows — Is there a theory ofthe continuum in which 
a new structural element appears side b) side with the 
metric such diat it forms a single whole together wadi 
the metric » If so, what are the simplest field-laws to 
which such a continuum can be made subject 1 And 
finally, are diesc field-laws jvctl fitted to represent the 
properties of the gravitational field and die electro- 
magnetic field? Then there is the further ijvesnon 
whether die corpuscles (electrons and protons) can be 
regarded as locations of particularly dense fields, whose 
movements arc determined by the field equations At 



present there is only one way of answering the first tlirce 
questions The space structure on which it is based 
may be described as follows, and the description 
applies equallv to a space of any number of dimen- 

Space has a Ricmanman metric Tins means that the 
Euclidean geometry holds good m the infinitesimal 
neighbourhood of every point P Thus for the neigh- 
bourhood of every point P there is a local Cartesian 
svstem of co-ordmatcs, m reference to \\ hich the metric 
is calculated according to the Pythagorean theorem 
If we now imagine the length I cut off from the positive 
axes of these local systems, we get the orthogonal 
local unit vector Such a local unit vector is to be found 
in every other point P' of space also Thus, if a linear 
element (PG or P'G ) starting front die pouits P or P', 
is given, then the magnitude of this linear element can 
be calculated by die aid of the relevant local unit vector, 
from its local co-ordinates by means of Pythagoras’s 
theorem There is therefore a definite meaning in 
speaking of the numerical equality of the linear 
elements PG and P'G' 

It is essential to observe now diat the local orthogonal 
unit vectors are not completely deterinmed by the 
metric For we can still select the orientation of die unit 
vectors perfeedy freely without causmg any alteration in 
the result of calculating the size of the linear elements 
according to Pythagoras’s theorem A corollary of this 
is that in a space whose structure consists exclusively of 
a Riemannian metric, two linear elements PG and P'G' 
«naT u\r tfsnrjrxrcu? wmV regain 1 nr ahnr* rrrjgmvmdr iVav 
not their direction, m particular, there is no sort of 
point in saying that the two linear elements are parallel 
to one another In this respect, therefore, the purely 


metrical (Riemanman) space is less rich m structure than 
the Euclidean 

Since v. c arc looking for a space which exceeds Rie- 
manman space m wealth of structure, the obvious dung 
is to ennch Riemanman space by adding the relation of 
direction or parallelism Therefore for every direction 
through P let there be a definite direction through P', 
and let tins mutual relation be a determinate one We 
call the directions thus related to each other “parallel ” 
Let this parallel relation further fulfil the condition of 
angular uniformity if PG and PK are two directions m 
P, P'G' and P'K' the corresponding parallel directions 
through P', then the angles KPG and K'P'G' (measur- 
able on Euclidean lines m the local system) should be 

The basic space-structure is tiiereb) completely 
defined It is most easil) described mathematically as 
follow — In the definite point P we suppose an orthog- 
onal unit v ector with definite, freely chosen orientation 
In every other pome P' ofspace we so onent its local unit 
vector that its axes are parallel to the corresponding axes 
at the point P Given the above structure of space and 
free choice in the onentauon of the unit \ ecror at one 
point P, all unit vectors are thereby completely defined 
In the space P let us now imagine an) Gaussian system 
of co-ordinates and that in every point the axes of the 
unit vector there are projected on to it This system of 
n* components completely describes the structure of 

This spatial structure stands, in a sense, midway be- 
tween the Riemanman and the Euclidean In contrast 
to the former, it has room for the straight line that is to 
say a line all of whose elements are parallel to each other 
in pairs The geometry here described differs from the 


Euclidean in the non-existence of the parallelogram If 
at the ends P and G of a length PG two equal and 
parallel lengths PP’ and GG* are marked off, P G is in 
general neither equal nor parallel to PG 
The mathematical problem now solved so far is this — 
What are the simplest conditions to which a space- 
structure of the kind described can be subjected i The 
chief quesnon which soil remains to be investigated is 
this — To what extent can physical fields and primary 
entmes be represented by solutions, free from singulari- 
ties, of the equanons which answer the former quesnon ? 

Notes on the origin of the general theory of Relativity - 

I gladly accede to the request that I should sav some- 
thing about the history of my own scientific work 
Not that I have an exaggerated notion of the importance 
of my own efforts, but to write the history of other 
men’s work demands a degree of absorption in other 
people s ideas which is much more in the line of the 
trained historian, to throw light on one’s own earlier 
thinking appears incomparably easier Here one has an 
immense pull over everybody else, and one ought not to 
leave the opportunity unused out of modesty 
When, by the special theory of relativity, I had arrived 
at the equivalence of all so-called inertial systems for the 
formulation of natural laws (1905), the quesnon whether 
“ ere not a further equivalence of co-Ordinate sys- 
tems followed naturally, to say the least of it To put 
U UX i ai \ 0 “ lc ^ only a relative meaning can be 

atta ed to the concept of velocity, ought we neverthe- 
less to persevere in treating acceleranon as an absolute 
concept 1 

From the purely "kinematic point of view there was 


no doubt about the relativity of all motion* whatever, 
but physically speaking, the inertial* sy ste m seemed to 
occupy a privileged posinon, which made the use of 
co-ordinate systems moving in other ways appear 

I was, of course, acquainted with Mach’s View, accord- 
ing to which it appeared conceivable that what inertial 
resistance counteracts is not acceleration as such but 
acceleration with respect to the masses (if die other 
bodies existing m die world There wa* something 
fascinating about this idea to me, but it provided no 
workable basis for a new theory 

I first came a step nearer to the solution pf the prob- 
lem when I attempted to deal with the lavV °f gravity 
within the framework 61 file special theory rfx drsavtzj 
Like most writers at the nme, I med to frame a f eld- 
law for gra/itation, since it was no longer possible, at 
least in any natural way, to introduce direct action at a 
distance, owing to the abolition of the notion of abso- 
lute simultaneity 

The simplest thing was, of course, to retain the 
Lsphciin scalar potential of gravity, and fP complete 
the equation of Poisson in an obvious manner by a term 
differentiated as to time m such a way that die special 
theory of relativity was satisfied The law of motion or 
the mass point in a gravitanonal field had also to be 
adapted to the speaal theory of relativity Th e P at h was 
not so wumstakably marked out here, sinctf die inert 
mass of a body might depend on the gravitational 
potential In fact this was to be expected on account or 
the principle of the inertia of energy . 

These investigations, however, led to a res u ’ r which 
raised my strong suspicions According xO classics 
mechanics the vertical acceleration of a body m die 


vertical gravitational field is independent of the hori- 
zontal component of velocity Hence in such a gravi- 
tational field the vertical acceleration of a mechanical 
system or of its centre of gravity works out indepen- 
dently of its internal kinetic energy !But in the theory 
I advanced the acceleration of a falling fiody was not 
independent of the horizontal velocity or the internal 
energy of a system 

This did not fit m with the old experimental fact that 
all bodies have the same acceleration in a gravitational 
field This law, which may also be formulated as the 
law of the equality of inertial and gravitational mass, 
was now brought home to me m all its significance I 
was in the highest degree amazed at its persistence and 
guessed that in it must lie die key to a deeper under- 
standing of inertia and gravitation I had no serious 
doubts about its strict validity, even without knowing 
the results of the admirable experiments of Eotvos, 
which — if my memory is nght — I only came to know 

I now abandoned as inadequate the attempt to treat 
the problem of gravitation, in the manner outlined 
above, within the framework of the special theory of 
relativity It clearly failed to do justice to the most 
fundamental property of gravitation The principle of 
the equality of ineraal and gran rational mass could now 
be formulated quite clearly as follows — In a homo- 
geneous gravitational field all motions take place in the 
same way as in the absence of a gravitational field in 
relauon to a uniformly accelerated co-ordinate system 
If this principle held good for any events whatever (the 
“pnnaple of equivalence”), this was an indication that 
the pnnaple of relativity needed ro be extended to 
co-ordmate systems in non-umform monon with re- 


spect to cacli other, if wc were to reach an easy and 
natural theory of the gravitational field Such reflec- 
tions kept me bus) from 1908 to 19 11, and I attempted 
to draw special conclusions from them, of which I do 
not propose to speak here For the moment the one 
important thing was the discovery that a reasonable 
theory of gravitation could only be hoped-for from an 
extension of the principle of relativity 

What was needed, therefore, was to frame a theory 
whose equations kept their form in the case of non- 
linear transformations of the co-ordmatcs Whether 
this was to apply to absolutely any (constant) transfor- 
mations of co-ordinates or only to certain ones, I could 
not for die moment say 

I soon saw that bringing in non-hnear transforma- 
tions, as the principle of equivalence demanded, was 
inevitably fatal to the simple physical interpretation of 
the co-ordinates — 1 e , that it could no longer be required 
that differentials of co-ordinates should signify direct 
results of measurement with ideal scales or docks I 
was much bothered by this piece of knowledge, for it 
took me a long time to see what co-ordinates in general 
really meant in physics I did not find the way out of 
this dilemma till 1912, and then it came to me as a result 
of the following consideration — 

A new formulation of the law of inertia had to be 
found which in case of the absence of a real “gravita- 
tional field with application of an inertial system' as 3 
co-ordinate system passed over mto Galileo’s formula 
for the principle of inertia The latter amounts to this 
A material point, which is acted on by no force, will be 
represented in four-dimensional space by a straight hne, 
that is to say, by a hne that is as short as possible or, 
more correctly, an extreme line This concept p re- 


supposes that of the length of a linear element, that is to 
say, a metric In the special theory of relativity, as 
Minkowski had shown, tins metric was a quasi-Euchdean 
one, 1 e , the square of the “lengdi” ds of the linear 
element was a definite quadratic function of the dif- 
ferentials of the co-ordinates 
If other co-ordinates are introduced by means of a 
non-linear transformation, ds* remains a homogeneous 
'function of the differentials of the co-ordmates, but the 
coefficients of this function (g^) cease to’ be constant 
and become certam functions of the co-ordmates In 
mathematical terms this means that physical (four- 
dimensional) space has a Ricmanman metric The 
timc-like extremal lines of this metric furnish the law 
of monon of a material point which is acted on by no 
force apart from the forces of gravity The coefficients 
(&iv) of this metric at the same nme describe the 
gravitational field with reference to the co-ordinate 
system selected A natural formulation of the principle 
of equivalence had thus been found, the extension of 
which to any gravitanonal field* whatever formed a 
perfectly natural hypothesis 
The solunon of the above-mentioned dilemma was 
therefore as follows — A physical significance attaches 
not to the differentials of the co-ordinates but only to 
the Ricmanman metric co-ordmated with them A 
workable basis had now been found for the general 
theory of relativity Two further problems remained 
to be solved, however 

(1) If a field-law is given m the terminology of the 
special theory of relanvity, how can it he transferred to 
die case of a Riemanman Vnetnc ? 

(2) What are the differential laws which determine 
the Ricmanman metric (lc, g^) itself » 



spcct to each other, if we were to reach an easy and 
natural theory of the gravitational field Such reflec- 
tions kept me bus) from 1908 to 1911, and I attempted 
to draw special conclusions from them, of which I do 
not propose to speak here For the moment the one 
important thing was the discovery char a reasonable 
theory of gravitation could only be hoped-for from an 
extension of the principle of relativity 

What was needed, therefore, was to frame a theory 
whose equations kept their form in the case of non- 
linear transformations of the co-ordinarcs Whether 
this was to apply to absolutely any (constant) transfor- 
mations of co-ordinates or only to certain ones, I could 
not for the moment say 

I soon saw that bringing in non-linear transforma- 
tions, as the principle of equivalence demanded, was 
inevitably fatal to the simple physical interpretation of 
the co-ordinates— -1 c , that it could no longer be required 
that differentials of co-ordinates should signify direct 
results of measurement with ideal scales or clocks I 
was much bothered by this piece of knowledge, for it 
took me a long time to see what co-ordinates m general 
really meant in physics I did not find the way out of 
this dilemma till 1912, and then it came to me as a result 
of the following consideration 

A new formulanon of the law of inertia had to be 
found which in case of the absence of a real “gravita- 
tional field with application of an inertial system as a 
co-ordinate system passed over into Galileo’s formula 
for the principle of inertia The latter amounts to this — 

A material point, which is acted on by no force, will be 
represented in four-dimensional space by a straight line, 
that is to say, by a line that is as short as possible or, 
more correctly, an extreme hnc This concept pre- 


Relativity and the Ether 

Why is it that alongside of the notion, derived by 
abstraction from everyday life, of ponderable matter 
ph) stcists have set die notion of the existence of another 
sort of matter, the ether ? The reason lies no doubt in 
those phenomena which gave nse to the theory of 
forces acting at a distance, and in those properties of 
light which led to the wave-theory Let us shordy 
consider these two dungs 

Non-physical thought knows nothing of forces 
acting at a distance When we try to explain our 
experiences of bodies by a complete causal scheme, 
there seems at first sight to be no reciprocal interaction 
except what is produced by means of immediate con- 
tact, e g , the transmission of motion by impact, pressure 
or pull, heating or inducing combustion by means of a 
flame, etc To be sure, gravity, that is to jay, a force 
acting at a distance, does play an important pan m every- 
day experience But smee the gravity of bodies presents 
itself to us in common life as something constant, 
dependent on no vanable temporal or spanal cause, we 
do not ordinarily dunk of any cause m connection with 
it and thus are not conscious of its character as a force 
acting at a distance It was not till Newton’s theory of 
gravitation that a cause was assigned to it , it was then 
explained as a force acting at a distance, due to mass 
Newton’s theory certainly marks the greatest step ever 
taken m linking up natural phenomena causally And 
yet his contemporaries were by no means satisfied with 
it, beam se rc seemed to contradict the prmapfc dented 
from die rest of cxpenence, that reciprocal action only 
takes place b) means of direct contact, not by direct 
action at a distance, without any means of transmission 


I worked on these problems from 1912 ro 1914 
together with my friend Grossmann Wc found that 
the mathematical methods for solving problem (1) lay 
read) to our hands in the infinitesimal differential cal- 
culus of Rica and Levi-Civita 
As for problem (2), its solution obviously needed 
invariant differential systems of the second order taken 
from guv We soon saw that these had ahead) been 
established by Riemann (the tensor of curvature) We 
had already considered the right field-equations for 
gravitanon two >ears before the publication of the 
general theory of rclaavit) , but we were unable to sec 
how they could be used m phjsics On the contrary, I 
felt sure that the) could not do jusnee to experience 
Moreover I believed that I could show on general con- 
siderations that a law of gravitanon invariant in relation 
to any transformanon of co-ordinates whatever was 
inconsistent with the pi-maple- of causation These were 
errors of thought which cost me two years of exces- 
sively hard work, until I finally recogmsed them as such 
at the end of 1915 and succeeded in linking up with the 
facts of astronomical experience, after having ruefully 
returned to the Riemanruan curvature 
' In the light of knowledge attained, the happ) achieve- 
ment seems almost a matter of course, and any intelligent 
student can grasp it without too much trouble But the 
years of anxious searching in the dark, with their 
intense longing, their alternations of confidence and 
exhaustion, and the final emergence into the light, — 
only those who have experienced it can understand 


other beyond die small deformations winch correspond 
to the waves ©flight 

This theory, also called the theory of the stationary 
luminiferous ether, derived strong support from the 
experiments, of fundamental importance for the special 
theory of relativity too, of Fizeau, which proved con- 
clusively that the luminiferous ether does not participate 
in the motions of bodies The phenomenon of aberra- 
tion also lent support to the theory of the quasi-ngid 

The evolution of electrical theory along the lines laid 
down by Clerk Maxwell and Lorentz gave a most 
peculiar and unexpected turn to the development of 
our ideas about the ether For Clerk Maxwell himself 

the ether was still an entity with purely mechanical 
properties, though of a far more complicated kind than 
those of tangible solid bodies But neither Maxwell 
nor his successors succeeded m thinking out a mechanical 
model for the ether capable of providing a satisfactory 
mechanical interpretation of Maxwell’s laws of the 
clectro-dynamic field The laws were clear and simple, 
the mechanical interpretations clumsy and contradictory 
Almost imperceptibly theoretical physicists adapted 
themselves to this state of affairs (which was a most 
depressing one from the pome of view of their mechan- 
istic programme) especially under the influence of the 
electro-dynamic researches of Heinnch Hertz Whereas 
they had formerly demanded of an ultimate theory 
that it should be based upon fundamental concepts of a 
purely mechanical kind (e g , mass-densities* velocities, 
deformations, forces of gravitation), they gradually 
became accustomed to admitting electric and magnetic 
field-strength as fundamental concepts alongside of the 
mechanical ones, without insisting upon a mechanical 



Man’s durst for knowledge only acquiesces in such a 
dualism reluctantly How could unity in our concep- 
tion of natural forces be saved ? People could -cither 
attempt to treat die forces which appear to us to act by 
contact as acting at a distance, though only making 
themselves felt at very small distances , this was the way 
generally chosen b) Newton's successors, who were 
completely under the spell of his teaching Or they 
could take the line that Newton's forces acting at a 
distance only appeared to act thus dirccdy, that they 
were real!) transmuted by a medium which permeated 
space, cither by motions or by an elasuc deformation of 
this medium Thus the desire for unity in our view of 
the nature of these forces led to the hypothesis of the 
ether It certainly led to no advance in the theory of 
gravitation or m physics generally to begin with, so 
that people got into the habit of treating Newton’s 
law of force as an irreducible axiom. But the ether 
hypothesis was bound always to play a part, even if it 
was mostly a latent one at first, in the thinking of 

When the extensive similadt) which exists between 
the properties of light and those of the clastic waves in 
ponderable bodies wras revealed in the first half of the 
nineteenth century, the ether h>po thesis acquired a new 
support It seemed beyond a doubt that hght was to be 
explained as the vibration of an elastic, inert medium 
filling the whole of space It also seemed to follow 
necessanl) from the polansabihty of hght that this 
medium, the ether, must be of the nature ofa solid body, 
because transverse waves are only possible in such a 
body and not in a fluid Thu inevitably led to the 
theory of the “quasi-ngiu ’ luminiferous ether, whose 
parts are incapable of any motion with respect to each 


by divesting the ether of its mechanical, matter of its 
electro-magnetic properties Inside material bodies no 
less than in empty space the ether alone, not atomically 
conceived matter, is the seat of electro-magnetic fields 
According to Loren tz the elemenrary parades of matter 
are only capable of executing movements, their electro- 
magnenc activity is entirely due to the fact that they 
carry electric charges Lorentz thus succeeded in 
reducing all electro-magneac phenomena to Maxwell’s 
equations for a field in vacuo 
As regards the mechanical nature of Lorentz’s ether. 

one might say of it, with a touch of humour, that 
immobility was the only mechanical property which 
Lorentz left it It may be added that the whole differ- 
ence which the special theory of relativity made in our 
conception of the ether lay m this, that it divested the 
ether of its last mechanical quality, namely immobility, 
How this is to be understood I will explain immediately 
The Maxwell-Lorentz theory of the electro-magneac 
field served as the model for the space-time theory and the 
kinematics of the special theory of relaavity Hence it 
satisfies the condmons of the special theory of relaavity , 
but looked-at from the standpoint of the latter, it takes 

on a new aspect If C is a co-orainate system m respect 
to which the Lorentzian ether is at rest the Maxwell- 

Lorentz equaaons hold good first of all m regard to C 
According to the special theory of relaavity these same 
equaaons hold good in exactly the same sense in regard 
to any new co-ordinate system C * which is in uniform 
translatory monon with respect to C We are now faced 
with the awkward quesaon why the system C, which is 
physically perfectly equivalent to the system C', should 
be distinguished from thelatter byassumingthattheether 
is at rest in respect to it Such an asymmetry of the 



interpretation of them The purely mcchamsnc view of 
nature was thus abandoned Tins change led to a dual- 
ism in the sphere of fundamental concepts which was in 
the long run intolerable To escape from it, the con- 
verse attempt was made to reduce mechanical concepts 
to deem cal ones The experiments with p-rays and 
high velocity cathode rays did much to shake confidence 
m the strict vabdity of Newton’s mechanical equations 
Heinrich Hertz took no 5 reps towards nungating this 
dualism Matter appears in his work as the substratum 
not only of \eIoanes, kinetic energy, and mechanical 
forces of gravity, but also of electro-magnenc fields 
Since such fidds are also found m a vacuum — ie, in 
unoccupied ether — the ether also appears as the sub- 
stratum of electro-magnenc fidds, ennrel) similar in 
nature to ponderable matter and ranking alongside lr 
In the presence of matter ic shares in the monons of the 
latter and has a velocity everywhere in empty space, 
the ether velocity nowhere dianges discontinuous!) 
There is no fundamental distinction between the Hert- 
zian ether and ponderable matter, which partly consists 
of ether 

Hertz’s theor) not only suffered from the defect that 
it attributed to matter and the ether both mechanical 
and electrical properties, wnth no rational connection 
between them, it was also inconsistent with the result 
of Hzeau’s famous experiment on the veloaty of the 
propagation of light in a liquid in motion and other 
well-authenticated empirical facts 

Such was the position when H A Lorentz entered 
the field. Lorentz brought theory into harmony wath 
experiment, and did it by a marvellous simplification of 
banc concepts He achieved this advance in the science 
of dectnaty the most important since Clerk Maxwell, 



by divesting the ether of its mechanical, matter of its 
electro-magncnc properties. Inside material bodies no 
less than in empty space the ether alone, not atomically 
conceived matter, is the seat of electro-magnetic fields. 
According to Lorentz the elementary parades of matter 
are only capable of executing movements ; their electro- 
magnetic activity is entirely due to the fact that they 
carry electric charges. Lorentz thus succeeded in 
reducing all electro-magnetic phenomena to Maxwell's 
equations for a field in vacuo. 

As regards the mechanical nature of Lorentz’s ether, 
one might say of it, with a touch of humour, that 
immobility was the only mechanical property which 
Lorentz left it. It may be added that the whole differ- 
ence which the special theory of relativity made m our 
conception of the ether lay m this, that it divested the 
ether of its last mechanical quality, namely immobility, 
How this is to be understood I will explain immediately. 

The Maxwell-Lorentz theory of the electro-magnetic 
field served as the model for the space-time theory and the 
kinematics of the special theory of relaavity. Hence it 
satisfies the conditions of the special theory of relaavity ; 
but looked-at from the standpoint of the latter, it takes 
on a new aspect If C is a co-orainate system m respect 
__ to winch the Lorentzian ether is at rest, the Maxwell- 
Lorentz equations hold good first of all in regard to C. 
Accordmg to the special theory of relaavity these same 
equations hold good m exactly the same sense m regard 
to any new co-ordinate system C\ which is in uniform 
translatorymoaon with respect to C. We are now faced 
with the awkward question why the system C r . which is 
physically perfectly equivalent to the system C\ should 
be distinguished from the latter by assuming that the ether 
is at rest in respect to it. Such an asymmetry of the 



theoretical structure, to which there is no corresponding 
asymmetry in the sjstem of empirical facts, is intolerable 
to the theorist In m) view the physical equivalence of 
C and C' with the assumption that the ether is at rest in 
respect to C but in motion with respect to C\ though 
not absolutely wrong from a logical point of view, is 
nevertheless unsatisfactory 
The most obvious line to adopt in the face of this 
situation seemed to be the following — There is no such 
thing as the ether The electro-magnetic fields are not 
states of a medium but independent realities, which 
cannot be reduced to terms of anything else and arc 
bound to no substratum, any more than are the atoms 
of ponderable matter This view is rendered the more 
natural by the fact that, according to Loren tz’s theory, 
electro-magnetic radiauon carries impulse and energy 
like ponderable matter, and that matter and radiauon, 
according to the special theory of relativity, are both 
of them only particular forms of distributed energy, 
inasmuch as ponderable mass loses its exceptional 
position and merely appears as a particular form of 

In the meantime more exact reflection shows that this 
denial of the existence of the ether is not demanded by 
the restricted principle of relativity Wc can assume the 
existence of an ether , but we must abstain from ascribing 
a definite state of motion to it, 1 e , w-e must divest it bv 
abstraction of the last mechanical characteristic which 
Lorcntz left to it Wc shall see later on that this way of 
looking at it, the intellectual possibility of which I shall 
try to make clearer by a comparison that does not quire 
go on afl fours, is justified by the results of the general 
theory of relativity 

Consider waves on foe surface of water Tfirrt are 


two quite different things about this phenomenon which 
may be described One can trace the successive changes 
which take place in the undulating surface where the 
water and the air meet One can also — with the aid of 
small floating bodies, say — trace the successive positions 
of the individual particles If there were in the nature of 
the case no such floating bodies to aid us m tracing the 
movement of the particles of liquid, if nothmg at all 
could be observed in the whole procedure except the 
fieenng changes m the posinon of the space occupied b> 
the water, we should have no ground for supposing that 
the water consists of particles But we could none the 
less call it a medium 

Something of the same sort confronts us m the electro- 
magnetic field We may conceive the field as consisting 
of lines of force If we try to think of these lines of 
force as something material in the ordinary sense of the 
word, there is a temptation to ascribe the dynamic 
phenomena involved to their monon, each single line 
being followed out through time It is, however, well 
known that this way of looking at the matter leads to 

Generalising, we must say that we can conceive of 
extended physical objects to which the concept of 
motion cannot be applied They must not be thought 
of as consisting of particles, whose course can be fol- 
lowed out separately through time In the language of 
Minkowski this is expressed as follows — Not every 
extended entity m the four-dimensional world can be 
regarded as composed of world-lines The special 
principle of relativity forbids us to regard the ether as 
composed of particles, the movements of which can be 
follow ed out through time, but the theory is not incom- 
patible with the ether hypothesis as such Only wc 


must take care not to asenbe a state of motion to the 

From the point of view' of the special theory of 
relativity the ether hypothesis does certainly seem an 
empty one at first sight In the equations of an electro- 
magnetic field, apart from the density of the electrical 
charge, nothing appears except the strength of the field 
The course of electro-magncnc events in a vacuum 
seems to be completely' determined by that inner law, 
and independent of other physical quantities The 
electro-magnetic field seems to be the final irreducible 
reality , and it seems superfluous at first sight to postulate 
a homogeneous, isotropic ethenc medium, of which 
these fields are to be considered as states 

On the other hand, there is an important argument 
m favour of the ether hypothesis To deny the existence 
of the ether is, m the last analysis, to deny all 
physical properties to empty space But such a view is 
inconsistent with the fundamental facts of mechanics 
The mechanical behaviour of a corporeal system floating 
freely m empty space depends not only on the relative 
positions (intervals) and veloanes of its masses, but also 
on its state of rotation, which cannot be regarded, 
physically speaking, as a property belonging to the 
sy stem as such In order to be able to regard die rotation 
of a system at least formally as something real, Newton 
regarded space as objective Since he treats his abso- 
lute space as a real thing, roranon with respect to 
absolute space is also something real to him Newton 
could equally well hase called his absolute space “the 
ether” , all that matters is that another and imperceptible 
ennty, in addition to observable objects, has to be 
regarded as real, in order char aeccleranon, or rotation, 
may be regarded as real 



Mack did indeed tty to avoid the necessity for postu- 
lating an imperceptible real entity, by substituting in 
mechanics a mean velocity with respect to the totality 
of masses m the world for acceleration with respect to 
absolute space But inertial resistance with respect to 
the relative acceleration of distant masses presupposes 
direct action at a distance Since the modem physicist 
does not consider himself entitled to assume that, this 
view brings him back to the ether, which has to act as 
the medium of inertial action This conception of the 
ether, to which Mach’s approach leads, differs m 
important respects from that of Newton, Fresnel and 
Lorcntz Mach’s ether not only conditions the behaviour 
of inert masses but is also conditioned, as regards its 
state, by them 

Mach’s notion finds its full development in the ether 
of the general theory of relativity According to this 
theory the metrical properties of the space- time con- 
tinuum in the neighbourhood of separate space-time 
points are different and conjointly conditioned by 
matter existing outside the region m question This 
spatio-temporal variability of the relations of scales and 
clocks to each other, or the knowledge that “empty 
space” is, physically speaking, neither homogeneous nor 
isotropic, which compels us to describe its state by means 
of ten functions, the gravitational potentials ^ v , has no 
doubt finally disposed of the notion that space is 
physically empty But this has also once more given 
the ether nonon a definite content — though one very 
different from that of the ether of the mechanical wav c- 
thmty aT Tbit, eshec o£ the. general theory of 

relativity is a medium which is itself free otdll mechanical 
and kinematic properties, but helps to determine 
mechanical (and electro-magnetic) events 


The radical novelty in the ether of the general theory 
of relativity as against the ether of Lorcntz lies in this, 
that the state of the former at every pomt is determined 
by the laws of its relationship with matter and with the 
state of die ether at neighbouring points, expressed in 
the form of differential equations, whereas the state of 
Lorentz’s ether, m the absence of electro-magnetic fields, 
is determined by nodimg outside it and is the same 
everywhere The ether as conceived by the general 
theory of relativity passes over into Lorentz’s if con- 
stants are substituted for the spatial functions describing 
its state, dius neglecting the causes conditioning the 
latter One ma) therefore say diat the ether of die 
general theory of relativity is derived by relativisanon 
from die ether of Lorentz 

The part which die new ether is destined to play in 
the physical scheme of the future is still a matter of 
uncertainty Wc know that it determines both materia) 
delations in the spacc-nmc continuum, c g , the possible 
configurations of solid bodies, and also gravitational 
fields, but wc do not know whether it plays a materia! 
part in the structure of the eleeme particles which 
constitute matter Nor do we know whether its struc- 
ture only differs materially from that of Lorentz’s in 
the proximity of ponderable masses, whether, in fact, 
the Geometry of spaces of cosmic extent is, taken as a 
whole, almost Euclidean Wc can, how c\ er, maintain 
on the strength of die relativistic cquanons of gravita- 
tion that spaces of cosmic proportions must depart from 
Euclidean behaviour if there is a positive mean density 
of matter, however small, in the Universe In this case 
the Universe must necessarily form a dosed space of 
finite size, this 512c being determined by die value of 
the mean density of matter 


If we consider the gravitational field and the electro- 
magnetic field from the standpoint of the ether hypo- 
thesis, we find a norahle fundamental difference between 
the two No space and no portion of space is without 
gravitational potential, for this gives it its metrical 
properties without which it is not thinkable at all The 
existence of the gravitational field is directly bound up 
with the existence of space On the other hand, a por- 
tion of space without an electro-magnetic field is per- 
fectly conceivable, hence the electro-magnetic field, m 
contrast to the gravitational field, seems m a sense to 
be connected with the ether only in a secondary way, 
since its formal nature is by no means determined by 
the gravitational ether In the present state of theory it 
looks as if the electro-magnetic field, as compared with 
the gravitational field, were based on a completely new 
formal motive, as if nature, instead of endowing the 
gravitational ether with fields of the electro-magnetic 
type, might equally well have endowed it with fields of 
a qtute different type, for example, fields with a scalar 

Since according to our present-day notions the pri- 
mary particles of matter are also, at bottom, nothing but 
condensations of the electro-magneac field, our modem 
view of the Universe recognises two realities which are 
conceptually quite independent of each other even 
though they may be causally connected, namely, the 
gravitational ether and the elcctro-magnetic field, or — 
as one might call them — space and matter 

It would, of course, be a great step forward if we 
succeeded in combining the gravitational field and the 
cleetro-magnctic field into a single structure Only so 
could the era in theoretical phy sics inaugurated by Fara- 
day and Clerk Maxwell be brought to a satisfactory dose 


The antithesis of ether and matter would then fade 
aviay, and the whole of physics would become a com- 
pletely enclosed intellectual system, like geometr), 
kinematics and the theory of gravitation, through the 
general theory' of relativity An exceedingly brilliant 
attempt in this direction has been made by the irtathc- 
matician H Weyl, but I do not think that it will stand 
the test of reality Moreover, in thinking about the 
immediate future of theoretical phj’sics we cannot 
unconditionally dismiss the possibdit> that the facts 
summarized in the quantum theory may set impassable 
limits to the field-theory 

We may sum up as follows — According to the 
general theory of relativity space is endowed with 
physical qualities, m this sense, therefore an ether 
exists Space without an ether is inconceivable For 
in such a space there would not only be no propagation 
of light, but no possibility of the existence of scales and 
clocks, and therefore no spatio-temporal distances in 
the physical sense But dus ether must not be diought 
of as endowed with the properties characteristic of 
ponderable media, as composed of particles the motion 
of which can be followed, nor may the concept of 
monon be applied to it 

The cause of the formation of v candcis in the courses of 
mers and of Beer's Lau , as it ts called 

It is common knowledge that streams rend ro curve 
m serpennne shapes instead of following die line of die 
maximum declivity of the ground It is also well known 
to geographers that die nvers of the northern hemi- 
sphere tend to erode dnefh on die right side The 
mersof die southern hemisphere behave in the opposite 


way (Beer’s law) Many attempts have been made 
to explain this phenomenon, and 1 am not sure whether 
anything I say in the following pages will be new to the 
expert , some of the relevant considerations are in any 
case known Nevertheless, having found nobody who 
thoroughly Understood the elementary principles in- 
volved, I think it is proper for me to give the following 
short qualitative exposition of them 
First of all, it is clear that the erosion must be stronger 
the greater the velocity of the current where it touches 
the bank in question, or the more steeply it falls to zero 
at any particular point of the confining wall This is 
equally true under all circumstances, whether the ero- 
sion depends on mechanical or on physico-chemical 
factors (decomposmon of the ground) We must con- 
centrate our attention on the circumstances which affect 
the steepness with which the velocity falls at the wall 
In both cases the as> mmctryhn relation to the fall in 
velocity in question is indirectly due to the occurrence 
of a circular motion to which we will next direct our 
attention I begm with a little experiment which any- 
body can easily repeat 

Imagine a flat-bottomed cup full of tea At the bottom 
there are some tea-leaves, which stay there because they 
are rather heavier than the liquid they have displaced 
If the hquid is made to rotate by a spoon, the leaves will 
soon collect in the centre of die bottom of the cup 
The explanation of this phenomenon is as follows — 
The rotanon of die hquid causes a centrifugal force ro 
act on it This in itself would give rise to no change m 
the flow of the hquid if the latter rotated like a solid 
body But m the neighbourhood of die walls of the 
cup the hquid is restrained by fnenon, so that the 
angular velocity with which it circulates is less diere 

than in other places nearer the centre. In particular, the 
angular velocity of circulation, and therefore the centri- 
fugal force, will be smaller near the bottom than higher 
up. The result of this will be a circular movement of 
the liquid of the type illustrated in Fig. r, which goes on 
increasing until, under the influence of ground fricnon, 
it becomes stationary. The tea leaves arc swept into 
tlie centre by the circular movement and act as proof 
of irs existence. 

Fig « 

The same son of tiling happens with a curving 
stream (Fig 2) At every section of its course, where 
it is bent, a centrifugal force operates in the direction of 

Ground Plan 

Fig 1 

the outside of the curve (from A to B) This force is less 
strong near the bottom, where the speed of the current 
is reduced by friction, than higher abosc the bottom. 
Tins causes a circular movement of die kind illustrated 
m the diagram Even where there u no bend in the 


river, a circular movement of the land shown in Fig 2 
will still take place, if only on a small scale and as a 
result of the earth’s rotation The Utter produces a 
Coriolis force, acting transversely to the direction of 
the current, whose Tight-hand horizontal component 
amounts to 2 v fl sin 9 per umt of mass of the liquid, 
where v is the velocity of the current, £2 the speed of 
the earth’s rotation, and 9 the geographical latitude 
As ground friction causes a diminution of this force 
towards the bottom, this force also gives rise to a circu- 
lar movement of the type indicated m Fig 2 
After this preliminary discussion we come back to 
the qucsnon of the distnbunoh of velocities over the 
cross section of the stream, which is the controlling 
factor in erosion For this purpose we must first realise 
how the (turbulent) distribution of veloanes takes 
place and is maintained If the water which was pre- 
viously at rest were suddenly set m motion by the 
action of an evenly diffused accelerating force, the dis- 
tribution of velocities over the cross section would be 
even at first A distribution of velocities gradually 
increasing from the confining walk towards the centre 
of the cross secnon would only establish itself after a 
time, under the influence of friction at the walls A 
disturbance of the (roughly speaking) stationary distri- 
bution of veloanes over the cross secnon would only 
gradually set in again under the influence of fluid fnc- 
non Hydrodynamics explains the process by which 
this stadonary dismbunon of veloanes is established in 
the following way — In a systemanc distnbunon of 
current (potential flow\ all the vortex-filaments are con- 
centrated at the walls They detach themselves and 
slowly move towards the centre of the cross-sccnon of 
die stream, distributing themselves over a layer of 


increasing thickness The drop in velocity at the con- 
taining walls thereby gradually diminishes Under the 
action of the internal friction of the liquid the vortex 
filaments in the inside of the cross section gradually get 
absorbed, their place being taken by new ones which 
form At the wall A quasi-staaonary distribution of 
velocities is thus produced The important thing for us 
is that the adjustment of the distribution of velocities 
till it becomes stationary is a slow process That is why 
relatively insignificant, constantly operative causes are 
able to exert a considerable influence on the distribution 
of velocities over the cross section let us now con- 
sider what sort of influence the arculir monon due to 
a bend in the nver or the Conohs-force, as illustrated in 
Kg 2, is bound to exert on the distribution of velocities 
over the cross section of the river The pamcles of 
liquid in most rapid motion will be furthest away from 
the walls, that is to say, m the upper part above the 
centre of the bottom These most rapid parts of the 
water will be driven by the circular motion towards die 
nght-hand wall, while the left-hand wall gees die 
water which comes from the region near the bottom and 
has a specially low velocity Hence in die case depicted 
m Kg 2 the erosion is nccessanl) stronger on the right 
side than on the left It should be noted that dm explana- 
tion is essentially based on the fact that the slow circu- 
lating movement of die wafer exerts a considerable 
influence on the distribution of velocities, because the 
adjustment of velocities which counteracts this conse- 
quence of the- circulating movement is also a slow pro- 
cess on account ofmtcmal friction 
We have now revealed die causes of the formanon of 
meanders Certain details can, however, also be- 
deduced without difficult} from these facts. Erosion 
20 S 


will inevitably be comparatively extensive not merely 
on the right-hand wall but also on the right half of 
the bottom so that there will be a tendency to assume 
the shape illustrated in Fig 3 
Moreover, the water at the surface will come from 
the left-hand wall, and will therefore, on the left-hand 
side especially, be moving less rapidly than the water 
rather lower down It should further be observed that 
the circular motion possesses inertia The circulation 
will therefore onl) achieve its maximum extent behind 
the position of the greatest curvature, and the same 
naturally applies to the asymmetry of the erosion 
Hence in the course of erosion an advance of the wave- 
lines of the meander-formation is bound to take place 

m the direction of the current Finally, die longer the 
cross section of the nver, the more slowly will the 
circular movement be absorbed by friction , the wave- 
line of die meander-formation will therefore increase 
with the cross secnon of the nver 

The Fleltner-sfup 

The history of scientific and technical disco\ery 
teaches us that the human race is poor in independent 
thinking and cream e imagination E\en when die 
external and scientific requirements for the birth of an 
— 09 


idea have long been there, it generally needs an external 
.stimulus to make it actually happen; man has, so to 
speak, to stumble right up against the thing before the 
idea comes. The Flettner-sbip, which is just now filling 
the whole world with amazement, is an excellent 
example of this commonplace and, for us, far from 
flattering truth. It also has the special attraction in its 
favour that the way m which the Flettner rotors work 
remains a mystery* to most laymen, although their 
action can be explained by mechanical forces which we 
all believe ourselves to understand instinctively. 

The scientific basis for Flettner s invention is really 
some two hundred years old. It has existed ever since 
Euler and Bernoulli determined the fundamental lav’s 
of the fnctionless motion of liquids The practical 
possibility of achieving it, on the other hand, has only 
existed for a few decades — to be exact, since we have 
possessed practicable small morors Even then the dis- 
covery did not come automadcally, chance and experi- 
ence had to intervene several times first 
The Flcttner-ship is closely akin to the sailing-ship in 
the way it works, as in the latter, the force of the wind 
is the only motive-power for propelling the ship , but 
instead of sails, the wind acts on vertical sheet-meta! 
cylinders, which are kept rotating b> small motors 
These motors only have to overcome the small amount 
of friction which the cylinders encounter from the sur- 
rounding air and m their bearings The monvc power 
for the ship is, as I said, provided by the wind alone 
The rota ting, c) hnders look like ship's funnels, only they 
arc several times as high and thick The area they 
present to the wind is some ten nmes smaller than that 
of the equivalent tackle of a sailing-ship 
“But now on earth do these rotating cy hnders pro- 


duce motive power?” the layman asks in despair 1 
will attempt to answer this question as far as it is 
possible to do so without using mathematical lan- 

In all motions of fluids (liquids or gases) where the 
effect of friction can be neglected the following remark- 
able law holds good —If the fluid is moving at different 
velocities at different points m a uniform current, the 
pressure is less at those points where the velocity is 
greater, and vice versa Tins is easily understood from 
the primary law of the motion If in a liquid in motion 
there is present a velocity with a right-ward direction 
increasing from left to right, the individual particle of 
liquid is bound to undergo acceleration on its journey 

Part de of Liquid 

Pressure _ 
on the left 

Fg 4 

from left to nghc In order that this acceleration may 
take place, a force has to act oil the particle in a right- 
ward direction This requires that die pressure on its 
left edge should be stronger than that on its right 
Therefore, the pressure m the* liquid is greater on the 
left than on the nght when the \eloaty is greater on 
the nght than on die left 

This law of the unerse ratio of the pressure to the 
velocity obviously makes it possible to determine the 
force of pressure produced by the motion of a liquid 
(or gas), simply b> knowing the distnbunon of veloci- 
ties in the fluid I will now proceed to show, by a 
21 1 

on the nght 


familiar example — that of the scent-spra) — how the 
principle cm be applied. 

Through a pipe slightly widened at its aperture A air 
is expelled at a high velocity by means of a compressible 
rubber bulb.. Thejer of air goes on spreading uniformly 
in all directions as it travels, in the course of which the 
velocity of the current gradually sinks to zero. Accord- 
ing to our law it is clear that there is less pressure at A, 
owing to the high ‘velocity, than at a greater distance 

Tig j 

from the aperture; at A there is suction, in contrast to 
the more distant, stationary air. If a pipe P, with both 
its ends open, is stood up with its upper end m die rone 
of high velocity and its low cr end m a vessel filled with 
a liquid, the vacuum at A will draw the liquid upwards 
out of the vessel, and the liquid on emerging at A wall 
be divided into tiny drops and whisked off by the 
current of air. 

After this preliminary canter let us consider die 
monon of a fluid around a Flermcr cy hndcr. 

Let C be the cylinder as seen from above. Let it not 
rotate to begin with Let the wind be blowing in the 
direction indicated by the arrows- It has jo make a cer- 
tain detour round the cylinder C, m die course of which 
ir passes A and B ar the same velocity. Hence the pres- 


sure will be the same at A and B, and there is no dynamic 
effect on the cylinder. Now let the cylinder rotate in 
the direction of the arrow P. The result is that the 
current of wind as it goes past the cylinder is divided 
unequally between the two sides, for the motion of the 
wind will be aided by the rotation of the cylinder at B, 
and hindered at A The rotanon of the cylinders gives 
rise to a motion with a greater velocity at B than at A 
Hence the pressure at A is greater than at B, and the 
cylinder is acted upon by a force from left to right, 
which is made use of to propel the ship. 


Fig 6 

One would have thought that an inventive bram 
might have hit upon this idea by itself, 1 e , without an 
extraneous cause However, what actually happened 
was as follows It was observed m the course of experi- 
ence that even m the absence of wind the trajectories 
of cannon balls exhibited considerable, irregular, and 
variable lateral deflections from the verncal plane 
through the initial direction of the shots This strange 
phenomenon was necessarily connected, on grounds of 
symmetry, with the rotation of the cannon balls, as 
there could be no other conceivable reason for a lateral 
asymmetry in the resistance of the air After this 
phenomenon had caused a good deal of trouble to the 


experts, a Berlin professor of physics, Magnus, dis- 
covered the right explanation about half way through 
last century. It is the same as the one I have already 
given for the force which acts .on the Fletmer cylinder 
in the wind ; only the place of the cylinder C is taken by 
a cannon ball rotating about a vertical axis, and that of 
the wind by the relative motion of the air with reference 
to the flying cannon bill. Magnus confirmed his 
explanation by experiments with a rotating cylinder, 
which was not materially different from a Fletmer 
cylinder. A little later the great English physicist Lord 
Rayleigh independently discovered the same phe- 
nomenon again in regard to tennis balls and also gave 
the correct explanation. Quite a short rime ago die 
well-known professor Prandd made an accurate experi- 
mental and theoretical study of fluid morion around 
Magnus cylinders, in the course of which he devised and 
earned out practically the whole of Flettner's invention. 
Prandtl’s experiments were seen by Fletmer, and sug- 
gested to him that this device might be used to take die 
place of sails. Who knows if anyone else would have 
thought of it if he had not*.